In-depth look at FOCUS and ASTROPHOTO - and how to tune it

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[@CuivTheLazyGeek]

To try everything Brilliant has to offer-free-for a full 30 days, visit brilliant.org/cuivlazygeek/. The first 200 of you will get 20% off Brilliant’s annual premium subscription.

[@michael.a.covington]

Nice video! Two key points about Bahtinov masks: (1) They can't be made of transparent material (e.g., by printing a pattern on glass) -- that would throw off the focus. They have to be completely open air in the transparent areas. (2) The shorter the focal length, the narrower and closer together the stripes need to be. A Bahtinov mask for a smartphone would probably require microscopic precision.

[@CuivTheLazyGeek]

Thank you!! I'm wondering about the telephoto lenses on recent smartphones though, I'd need to check the Bahtinov generator!

[@ffwrnais]

Fascinating! I thought I knew a fair bit about focusing but I now understand a lot more.

[@CuivTheLazyGeek]

Glad this is teaching new stuff :-)

[@peterv8]

I found something out concerning the Bathinov Mask. When your collimation isn't perfect, it will NOT give a perfect focus when the spikes are even. When you focus visually, it will be better. So if your refractor isn't perfect collimated, you better focus visually.

[@blackbear92201]

A super-informative video about achieving focus. thanks for posting! :D

[@damiengalanaud3817]

Excellente vidéo Cuiv, très claire et très informative.

[@siegfriednoet]

Outstanding video Quiv ! Although I knew most of it Quiv, I really was listening with open mouth to hear you passionate explanation about this topic. You would be a great teacher Quiv, well I really should say that you are a great teacher Quiv !

[@CuivTheLazyGeek]

Thanks so much Siegfried! And yes I do love teaching so that's great for me :-)

[@guyjordan8201]

Half flux is new to me. It’s great to learn new things. Please keep up the good work, you make me less dumb ha ha

[@CuivTheLazyGeek]

That's what I aim to do :-)

[@ColeRees]

You’ve got a sponsor?! Congratulations, Cuiv! You’ve made it. Hope to join you soon!

[@sneakerset]

Acronym-a-rama. Thanks for detailing this aspect of AP imaging, Cuiv !

[@CuivTheLazyGeek]

My pleasure!

[@ekalbkr]

Thanks Cuiv! The geek side of you is superior to all the other AP channels. Years, and years ago, I struggled with quadratic equations, largely because i did not understand the 'why' of how it works. I was told to just 'follow the formula', which in many things, never worked for me. Your detail and enthusiasm scratches the right spot for me. These 'skull sessions' are priceless! Hmmm, maybe that means I should join your channel...

[@CuivTheLazyGeek]

I'm so glad my videos have been helpful! And don't worry about membership, only if you have the means and feel like it ;)

[@CrownOfThornss]

This was so helpful! Thank you:)

[@johannesofner2954]

To quote legendary Mr. Spock - FASCINATING! Thx Cuiv for another great lecture👏

[@CuivTheLazyGeek]

Thanks Johannes! Glad you enjoyed! This kind of video gets fewer views, but I think they're both fun and important!

[@Dak3]

Another great video, thank you Cuiv!

[@CuivTheLazyGeek]

Thank you Dake!

[@urmymusemusic4825]

Very helpful video Cuiv. I may try renovation on my newtonian when I get some spare time !

[@CuivTheLazyGeek]

Thanks!

[@deep_space_dave]

You just reminded me why I need to use a bahtinov mask on my guide scope. All this time I've been doing FWHM when all I had to do was aim at 1 bright star and use the bahtinov mask 🤦 Thanks for the video and Clear Skies!

[@TevisC]

Actually, having slightly out of focus helps phd2 guide better.

[@CuivTheLazyGeek]

Yep the old recommendation for guide scopes was to be slightly out of focus, but that wasn't correct :)

[@mikemccann8822]

Interesting! Why isn’t that so anymore, new algorithm? I was having poor tracking with OAG recently, I think mainly because there could be large temperature changes between evening and wee hours of the morning, as much as 20°C. I added a guidescope to see if it improves. My RC fl is 2800mm and the guidescope is 1300 (102mm Maksutov). Now I’m experiencing the best guiding I’ve ever had. What I noticed with the OAG was depending on filter and temperature the limited field of view the brightest star was often chosen and out of focus the star blob grew. Grew to the point while watching I could see phd2 changing its point across that bright blob often. Sending lots of corrections to the mount. Through this learning process I’ve concluded: - check focuser at beginning and end temperature and through all filters; make sure the guider doesn’t lock into the brightest and fattest star. The problems I have with OAG on the 2800mm fl I don’t have on my scope with 910mm because more stars.

[@DrewJEvans44]

Well done, Cuiv. Very in depth explanation.

[@CuivTheLazyGeek]

Glad you enjoyed!

[@taurus7228]

Awesome stuff. The 24 mins contains way more information. Thank you 🙏 ashv

[@CuivTheLazyGeek]

Thanks for the feedback!

[@naegeleh]

Very informative!!! Really important informations!! Thanks a lot!!

[@CuivTheLazyGeek]

Glad it was helpful!

[@EMANUELETONUCCI]

Fantastic video, thank you very much!!!

[@CuivTheLazyGeek]

My pleasure, glad you liked it!

[@ssrattus]

Interesting! Thanks Cuiv.

[@CuivTheLazyGeek]

Glad you liked it!

[@Bobi_203]

A big greeting to you, I would like to ask if I make a Bahtinov mask on a 3D print according to the specifications of my telescope, will it focus better than the commercial one from the store or will there be no difference.

[@davidwillis5396]

Great vidio Cuiv

[@user-lt9py2pu6u]

Interesting. I have just upgraded my Red Cat 51 and 81 GT scopes with auto focusers and hope to be able to test them over the comming week. Trying to manually refocus at 3am at -10°C last winter was nota lot of fun. I mainly image with narrowband filters so a refocus is also necessary at each filter change. I have been using the focusing assistant in Sharp Cap for mono imaging and a Bathinov mask when using my DSLR with APT. I have just downloaded NINA but have not used yet.

[@CuivTheLazyGeek]

Autofocusing really changes the game!

[@ShevillMathers]

Clive, my astronomy friend, I have to correct you on a minor point. Light from a curved primary mirror does not come to focus on the secondary mirror, the secondary flat mirror intercepts & turns the beam through 45 degrees which comes to focus at the film plane of a camera or the inner field lens of an eyepiece. Greetings from Tasmania Australia 🔭👍🇦🇺 My comments aimed at the newcomers to setting up a Newtonian telescope, not yourself of course. No doubt someone would be trying to get focus on the secondary, I know this happens from my own past teaching experiences.

[@CuivTheLazyGeek]

Hahaha yes of course Shevill you are right, thank you! I wanted to quickly explain why we'd see a shadow/doughnut shape and can't go into the full details!

[@luboinchina3013]

I have a big dilemma right now. Is it worth to buy EAF for my 8HD? The teleacope has two mirror lock screws. If the mirror is locked, little adjustments to the focus will shift star position. It won't be centered anymore. Ideally for focusing you would unlock the mirror and after focus you would lock it so the main mirror would not shift possition through the night. But how to do it automatically? I was thinking about linear focuser, but that would increase the back focus distance and make it worse.... HELP

[@CuivTheLazyGeek]

Yeah there's no automated way to unlock the primary afaik - when I had the 8HD, I had gotten a moonlite focuser for it so I could keep the mirror locked! With the F7 reducer I found a way to fit the Moonlite and the Celestron OAG into the imaging train while still having perfect back focus (there's a thread somewhere on CN where I describe how to do that) If you use the EAF, I think keeping the mirror locks off would be the right way to go...

[@ericgilson9060]

I bet you could use a fine kitchen sieve or the right window screen material to get you phone to show them.

[@CuivTheLazyGeek]

Probably

[@peterv8]

Did they give mister Bathinov the nobel prize yet? 😁

[@bakerfx4968]

What about making an ascom temperature gauge to attach to the rig that triggers an autofocus only once the ambient temps drop a degree? Would something like that be possible?

[@CuivTheLazyGeek]

That's already possible! Many focusers have an optional temperature gauge accessory (and sometimes an internal one like the EAF, but that's not precise) and you can request AF every x degrees. Or even better, measure the focus deviation with temperature, have it as a function and continually adjust the focus with it.

[@bakerfx4968]

@@CuivTheLazyGeek really cool! Thanks for the info, Cuiv!

[@tubedude54]

Every now and then, usually during this very type of discussion, I have thought that camera sensor manufacturers could put out sensors that are curved to conform to the standard types of telescopes out there. They could probably come up with 3 or 4 different curves that would fit most telescope designs and make chips based on those curves. Even if you had a scope they didn't specifically make a chip for you could get one that would be better than just using a flat chip.

[@CuivTheLazyGeek]

Sony's been working on that :-) although obviously not with telescopes in mind but normal camera lenses. Main problem would be that all camera lenses would need to be redesigned to fit the sensor's curve - which would indeed need to be used judiciously

[@tubedude54]

@@CuivTheLazyGeek That's interesting! All they need is like 3 'curves' to fit F ratios of 2,6, and 11 and it would cover 90% of the scopes out there. When you ordered a camera you would get a closest fit for your scope. I realize astronomy is not a major concern of the chip makers but Canon did accommodate us with a camera without an IR filter.

[@timpatton3948]

Remember the like button. It helps to grow the channel .

[@CuivTheLazyGeek]

Yesssss thank you!

[@user-rs2ys1wr8d]

شي جديد جميل

[@anata5127]

In time Bahitov created mask, nobody could patent nothing in Soviet Union.

[@ctyragdoll]

Before Bahtinov, we had a variety of different masks to use, none as good as the Bahtinov. I used to use a three hole "Hartman" mask for film photography back in the day. Some camera makers also offered focus screens that were also, tailored to astrophotography.

[@tyrantworm7392]

It was 2005 acording to Wiki. Could nothing be patented in Russia at the time, and have things changed?

[@anata5127]

@@tyrantworm7392 Maybe changed little bit, but not a lot. I am sure Putin can patent anything.

[@PlandemicSeries-com]

The "Soviet Union" didn't exist in 2005... Pavel Bahtinov simply didn't realise exactly what he invented and how popular it would become.

[@anata5127]

@@PlandemicSeries-com It is common nativity during and after Soviet Union. It is very tough to change mentality in 10-15 years.