Breaking the Rules of Astrophotography: Surprising Results from Pairing an ASI2600 and RedCat51

In this video I experiment with a combination of telescope and camera that should be incompatible with each other. I paired my ASI2600MM Pro APS-C sensor with the William Optics RedCat51 which should be incompatible due to under sampling issues because of the wide angle of the lens and the pixel size of the camera, however, in this video you will see that this might not be an issue after all.
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[@astrojourneyuk]

A lot of people have mentioned drizzling so, here is how to drizzle in PixInsight: astrojourneyuk.com/how-do-i-drizzle-in-pixinsight

[@JonnyBravo0311]

People make way too big a deal of the sampling rate. End up making poor purchase decisions because some calculator on the internet told them that OH NO!!! YOU'RE UNDER SAMPLED!!! Meh. You can make absolutely fantastic images from under sampled data. Plenty of APODs have been created from setups that are under sampled. Glad to see someone showing the kinds of results attainable from using what is considered a "poor" combination of gear :).

[@astrojourneyuk]

Thanks for your comment. My situation I looked at one of those under / over sampling calculators and thought that my camera wasn't suitable at the time. Although back when I got the ASI183 for the RedCat I "needed" a One Shot Colour (OSC) camera anyway so I could have 2 fully working setups, but this experiment did prove to myself it wasn't as bad as I thought it was. Thanks for stopping by and commenting.

[@skygazr33]

As an owner of a RedCat 51 and an ASI2600MC, I agree with your assessment completely. I always dither and drizzle. And now with BlurXTerminator, stars are looking even better.

[@astrojourneyuk]

Thank you for sharing your views too. It’s always good to hear others experiences.

[@stevenickolls8016]

Thanks for your video on this subject. Pleased you've come to a conclusion over 'under sampling'. I have never worried about under sampling, and think often astrophotographers obsess over too many first world issues. By all means use other combinations of optics and sensors and mosaicing to image wide nebulae but being undersampled doesn't hurt and in these days of StarNet++ we remove the tiny stars anyway. Cheers and clear skies.

[@astrojourneyuk]

Great point, maybe sometimes we unnecessarily pursue perfection which just costs us more money by getting additional kit. In my case it just seemed on the face of it I should get a different camera but in reality wasn’t necessary. Hopefully, this video means that others will save some money! :)

[@woody5109]

ASIAIR has so many features, every time I watch one of your videos I discover more, thanks for sharing

[@astrojourneyuk]

I’m planning a full walk through next time it’s clear to try and show everything. There’s definitely a lot there and it will be great to see how the CAA will work with the ASIAIR so expect another update to support that.

[@jpastroguy]

I think your conclusions are perfectly legitimate. Slight under sampling or over sampling is not a significant issue for your average amateur astrophotographer. It was nice to see the data. Funny coincidence that I viewed this video while visiting my in-laws house! Nice video!

[@astrojourneyuk]

Yeah, it doesn’t seem to be a massive issue at the end of the day. I hope you had a good trip and thanks for watching and commenting.

[@astrotherapist]

Your video is really informative. This equipment is something I just can't afford, but I kept watching to the end of the video because you did such a good job! Fantastic final image!

[@astrojourneyuk]

Thank you Paulette, to be honest I'm not sure I can afford it either! I'll be paying for the AM5 and the ASI2600 for a couple of years! :( Hopefully, I'll get a good amount of use out of them in the meantime.

[@Astrobloke]

Very nice rig and a little drizzle of the data would soon sort out the undersampling. As you say it only shows if you crop right in.

[@astrojourneyuk]

Thanks Glenn, I forgot to mention this so it’s good that you’ve raised it.

[@Astrobloke]

@@astrojourneyuk if its good enough for Hubble its good enough for you Marn

[@astrojourneyuk]

Hubble drizzle their data? I didn’t know that!

[@Astrobloke]

@@astrojourneyuk Drizzle (or DRIZZLE) is a digital image processing method for the linear reconstruction of undersampled images. The method is normally used for the combination of astronomical images and was originally developed for the Hubble Deep Field observations made by the Hubble Space Telescope.

[@astrojourneyuk]

Nice one, thanks Glenn. It looks like your observatory is coming along nicely. I’m expecting more clouds when you’re done. 😀

[@SimonsAstro]

Hey Marc, good video mate. I also have the Redcat 51 and two 2600’s colour & mono! I won’t be buying another camera just for the Redcat thought! As you say, so long as you’re not displaying your images on a bill board, who cares! They look fine to me at normal size! Clear skies mate👍

[@astrojourneyuk]

Thanks Simon for your view on this too. I think I could now sell a couple of cameras, I have too many anyway. :)

[@BigBadLoneWolf]

I recently bought a redcat51 and paired it with the zwo 533mcpro, which has the same pixel size as the 2600, and I am happy with the results

[@astrojourneyuk]

The 533 is a nice camera with no amp glow which is great, as long as you're okay with the square format sensor, which to be honest I've never found to be an issue.

[@jimb7931]

As stated by a few people below, dithering and applying drizzle data will make those blocky stars sharper.

[@astrojourneyuk]

Thanks as well Jim. The best thing about this hobby is the community and helping people out. Thanks.

[@seriousbassface]

Thank you for this, I just grabbed the ASI2600 today. I wanted to shoot the comet with it and was gonna use my old filter wheel till I can get new filters. Well I spaced the connections to the filter wheel with my other telescope which wouldn't work. So this is allowing me to still try out the new camera tonight at least. Will also give me more crop room for the vignetting so probably good in the long run anyways.

[@OldGirlPhotography]

I know this was a while ago, but I'm just looking at this issue now and I completely agree - the acceptability of the results depends on what you will use the image for, particularly if posting on social media is the goal. That said, I see the fully processed image at the end of the video and even on a computer screen with KZbin's compression algorithm at play, I do detect a noticeable difference in depth and definition in that image compared to others I've seen from "matched" cameras and scopes from other astrophotographers. So not totally without merit to consider sampling rates.

[@astrojourneyuk]

Thanks for the comment. It’s a good point about social media, if that’s your place then no real need to drizzle. I don’t print enough, but really should.

[@BigBadLoneWolf]

I use my 533 with my redcat51, which has the same pixel size. as long as you dither and drizzle, the results are fine

[@JoeBob79569]

Breaking the rules, or at least testing them, is one of my favourite things to do. Because I find that just blindly following the rules means you probably don't really know why you are following them in the first place, and so you could be doing something needlessly. Like refocusing after every single shot, or taking darks, biases, flats dark flats, after every session, because the internet told you so..

[@michaellewis5921]

That's what drizzling is for. Rounds out the small stars a bit, plus gives you something that can be printed large, if that is your intention.

[@jonathanpearceff]

I use a 533MC-Pro with my RedCat51 and get the same under sampling as you. I just do a x2 drizzle when stacking in WBPP. That sort of fixes the issue. What I do find after the drizzle is when zoomed into some of the smaller stars, they appear as small doughnuts, but on the undrizzled version they are you small blocky stars. Must be something to do with the way drizzle works. I haven’t been able to solve it and should really post a question on the PixInsight forum. The way I get round it is to use the stars from the undrizzled image (I extract them and do normal processing on them and then rescale 200% and combine with the x2 drizzle image).

[@astrojourneyuk]

Thank you for sharing your processes with us. It’s interesting that drizzling isn’t the only part of the answer here. Thanks I’ll have a look and see what I see.

[@davewilton6021]

Yes, I've used my 2600 with my Redcat and drizzling fixes any issues caused by undersampling. (I haven't seen any doughnutty stars; not sure what's happening there.) Also, the BlurXTerminator plug-in for PixInsight can fix much of the undersampling problem with stars. But the great thing about drizzling is that it not only fixes blocky stars-that's only the most obvious issue-it gives you better resolution on the other objects as well. As to undersampling not being an issue at all, that's often the case when viewing images on the screen, and especially over the crappy resolution of social media apps, but if you make a high-quality print the blocky stars become readily apparent even to a casual viewer. Whether or not its a problem depends on how the image is to be viewed.

[@astrojourneyuk]

Interesting that BlurXterminator helps too and thanks for sharing your drizzling experience too.

[@billwright9518]

Great video, didn't know about checking the star size in the asiair, that's a great tip, many thanks. 👍

[@astrojourneyuk]

No problem Bill.

[@mikelockwood2104]

good job again sir.....great experiment. Thank you for sharing

[@astrojourneyuk]

Thank you, no problem.

[@timburgess1528]

That’s very interesting thanks, as you say I also got the 183MC Pro because I was starting out and thought I should follow all advice, but as you nicely show it really seems a non-issue. It’s probably the same sort issue as when I was told that I really should be buying oxygen free interconnect between my CD player and amp 🤣🤣. Very useful thanks!

[@astrojourneyuk]

Ahhh the old speaker cable advice. I always thought that yes, it probably is better but if you can’t hear the difference or can compare it side by side does it matter. I should really have linked to the image too so people can see for themselves. As others have said Drizzling can fix this too. Best of both worlds.

[@barneyrubble9309]

I know this an old vid but this is exactly the set up im aiming for.

[@legacysearches4481]

I think software may help and now that I have both 2600 cameras I think I am going to experiment with gain or exposure time to see if maybe I can overexpose just a bit to fill the pixels. I don’t know but I can try it and find out.

[@wildweedle6012]

Did you say which filter set you are using?

[@LeonHulstroem]

Drizzle when undersampled helps a lot 👍👍

[@astrojourneyuk]

That is right, I should maybe do a follow up that shows the difference for completeness.

[@Thommy78]

Great gear, I have/had similar setup but an Skywatcher 50ED for first experiences. And I can say it is really amazing what you can squeeze out of that. And then with the redact it must be fantastic.

[@astrojourneyuk]

I do absolutely love the RedCat such a well designed and very capable scope.

[@nikaxstrophotography]

drizzling will sort out undersampling

[@astrojourneyuk]

Very true and thank you for sharing. I should have mentioned that in the video. Although the thing I partly wanted to point out was that on screen it’s not really an issue.

[@MakeAMark]

Yes -- I have a similar issue with my ASKAR FRA300pro and ASI 2600mc-pro. If I drizzle I get much improved stars. But I agree that if your target is a large nebula or similar, the undersampled stars, at least on my system, are not really an issue.

[@carolsantulis1990]

I Have the same scope/camera and I love it. I get enough resolution to modestly crop on galaxies. I was scolded by someone that proffessionally builds telescope rigs, that this is very under sampled. Well I wanted a large sensor for the RedCat51, so APS-C it was. My stars look fine if you don't pixel peep at 200%.

[@astrojourneyuk]

That is true, although I guess if you do need to crop in then you might run the risk of seeing blocky stars. As lots of people have mentioned, drizzling could be the answer without needing to get a different camera.

[@carolsantulis1990]

@@astrojourneyuk Yes, I need to learn more about drizzling. I thought you were going to mention binning. I have to learn about doing that in software too.

[@astrojourneyuk]

To be honest I’ve never tried drizzling as I’ve not needed too. It does look like it’s just an option when stacking in PixInsight so time to have a look. Binning is just an option during image capture and can be done on the ASIAIR and other image capture software, only worth it if you are oversampled I believe.

[@cdh79]

thanks, I am just building a spacecat setup and will get myself the 2600mc-pro (I already have a few mono CCD's, so I want to try a OSC for once).. In regards to undersampling: I've been undersampling with some of my CCD's for ages (i.e a QSI683wsg on a Tak FSQ-85) and dithering and drizzle has always worked well for me. About AM5 guide-settings, there's great info on the Zwo forums from user "w7ay" that those harmonic drives are best guided with very short impulses (0.5sec) and low aggressiveness and low max ra/dec values (not more than 200ms) and he explains it into very deep technical detail.. not sure if you have seen this, but it was an interesting read.. not that it would really make any difference for your setup with the redcat and the 2600, as 0.7" RMS should be more than sufficient, but it may be handy to look into when trying scopes with longer focal length or cameras with much smaller pixel size.. one of them called "Getting the best performance from my AM5" and then there's a link in the first message to another thread (something with high backlash) where he goes into very deep technical detail of the AM5 as well. Can highly recommend this..

[@astrojourneyuk]

Thanks a lot for the information on the AM5, I'll give it a test and see what happens. Naively I assumed that the ASIAIR would default whatever settings were best but let's see what happens with tweaking the settings. Good luck with the 2600MC Pro, if money were no object I'd love one of these for the evenings where I'm feeling impatient and not up to using the mono camera. (Not that it really makes a difference in reality from an integration time perspective). Thanks again!

[@astrodysseus]

well if you had a bad seeing, you were not under sampling that much. in any case, under sampling is just another way to say that you are not capturing the full resolution you could. you still get an image in the end and the 2600 is a good camera, so you still get a good image. not much surprising here ? admittedly, i watched the video very quickly so I may have missed your point

[@lcmattern]

I guess a question i have is, how much is that setup cost together? What is the difference shooting an image with no filter vs. a filter, or was this done because it is a bw camera instead of rgb? I'm new to this whole thing and have been reading i to it.

[@Astro_Shed]

Very interesting…thanks for another great video…👍🏻

[@astrojourneyuk]

Thank you for stopping by, watching and commenting. It’s a great encouragement.

[@Astro_Shed]

@@astrojourneyuk your welcome, I have watched many of your videos, and subscribed some time ago, and because of you and others I have started my own chanel now…👍🏻

[@astrojourneyuk]

Cool, I’ll take a look and subscribe! Good luck with your channel.

[@ballage2023]

oh the dream rig! gj mate

[@astrojourneyuk]

It’s a nice combo for sure. I definitely won’t be buying anything more for a long time.

[@ballage2023]

@@astrojourneyuk yeah I can imagine I have an old black HEQ5, pimped w rowan belt and new bearings with the redcat, eaf, asiair and zwo533 color+L-extreme also looking pretty great and makes beautiful photos:)

[@swagonman]

Well, it might be undersampling if the RedCat were diffraction limited. But little scopes like this just aren’t diffraction limited. Take a look at William Optics published spot diagrams. They are better than most competitors, but larger than the theoretical airy disk of a hypothetical diffraction limited OTA. So, I think your sampling ratio is right in the ball park.

[@craiglowery4427]

Cool experiment. How would galaxies look with your rig?

[@astrojourneyuk]

With this combination they would likely be pretty small. M31 might have a fighting chance but I think a lot more focal length would be needed for most galaxies.

[@gspinin]

Any tilt issues with this set up?

[@astrojourneyuk]

Not that I'm aware of to be honest. I didn't tweak it at all from purchase and the stars look good to me.

[@carlosc7631]

Very Good!

[@astrojourneyuk]

Thanks!

[@baz_astra]

I've come to realize that with Drizzle + BXT it literally doesn't matter any more.

[@johnmheaton]

If we had the ability to zoom in with the MK1 eyeball, it could be an issue I guess? That upgrade is some way off - but I'm sure "ZWO Medical" would sell it if it happens! 😉

[@astrojourneyuk]

Could you imagine that would be cool. I wouldn’t want to be an alpha tester though and definitely worth waiting for version 2. 😀

[@woody5109]

I’m new to this hobby, what’s “binning”?

[@astrojourneyuk]

In short binning is when you combine the adjacent pixels of your camera sensor together to make a larger pixel. It increases the signal to noise ratio but has the impact of reducing the resolution of the final image significantly.

[@davewilton6021]

To add to what AstroJourneyUK said, binning is helpful when you're oversampled (the opposite of undersampling; more pixels than you need to resolve at the theoretical limit of the system). When you're oversampled, binning reduces file size without compromising on resolution. Many astro cameras allow you to set the bin rate, typically 2x or 3x. Or you can bin in post-processing.

[@astrojourneyuk]

Thanks Dave for adding that. I forgot to mention the why! 🙈😂

[@evemitchellanderson]

I have the eos ra. You know the one THAT TREVOR USED AND SAID WAS SHARP! Apparently someone likes to lie to boost sales. The eos Ra is not a good match for the red cat 51.

[@astrojourneyuk]

I've not looked at the pixel size of the Ra sensor but the physical size of the sensor should give you a wide field of view. I have been playing with drizzling with the image I took for this video and it helps to improve things. Did you find issues with the Ra and the RedCat then? I do know of a lot of people that tend to use the DSLR and RedCat51 combo though.

[@robertgrenader858]

Good overview, but this is really a "how many angels can fit on the head of a pin" issue. If you are satisfied with your images, that is all that matters. RedCats rule!

[@astrojourneyuk]

It is very true. Turns out those stars can be pretty small, just a couple of pixels. You’re right there, RedCat rules!!!!

[@romans9249]

Drizzling + upsampling = sorted

[@astrojourneyuk]

Summary of the whole video in one comment. :)

[@rvoykin]

The 2600 cameras really start to shine around 500mm+

[@astrojourneyuk]

That’s a good point. I had a SkyWatcher EvoStar 80ED Pro with a reducer at 510mm and the images (the few that I’ve managed to get this year) look beautiful but they were of targets around Orion and I’ve run out of time with that part of the sky now. :(

[@curtishorn1267]

Congrats on discovering what we EAAers have known for years.

[@astrojourneyuk]

Yeah I’m a slow learner and like to see things for myself. 😀😀😀

[@richardjakobson7094]

Interesting video thanks. I have the same combination of a Redcat 51 and ASI 2600MMPro. Like you I have found the undersampling not a significant issue with my images unless I zoom right in. Even then, if I dither when imaging and drizzle when processing the "blocky" stars are improved considerably. Apparently we are not alone and the Hubble has an issue with undersampling. This prompted the NASA processors to develop drizzle.

[@astrojourneyuk]

That's poor planning on NASA's part to not use their telescope and camera combination on one of the sampling checking sites. :D I just looked up the effective focal length, it's 57m!!!!

[@southbronxny5727]

It's perfect......just stack those subs.

[@astrojourneyuk]

😀

[@hael8680]

You'd be better off to get an autofocuser than buying another camera 😉

[@astrojourneyuk]

Nooooo, there was me thinking I didn’t need to buy anything and now you’ve mentioned that. 😂😂😂

[@hael8680]

@@astrojourneyuk Seriously, that's a huge improvement. You end up saving time while imaging and are guaranteed good focus. Once your system is set, an autofocus run takes 2 min. Some systems are cheap and have no backlash to deal with.

[@astrojourneyuk]

I do love the EAFs I completely agree. I have one each on my other scope but not on the RedCat yet. I need to design and make a bracket.

[@sarahjanereilly9335]

@@astrojourneyukBlack cat is great - takes the ASIAir too!