Having hyperstar star shape issues? This might help.

[@PhotonVoyage]

1. Colimate your telescope precisely using the Starizona manual. 2. Backfocus can be a problem, especially if you are using a filter. You must add a third of the filter's thickness, and most filters are 2mm, so about 0.66mm of focus will be off, which is more than 0.5mm, which is an okay standard. 3. Autofocuser must be set properly by managing a backlash compensation... Do this and let us know.

[@Dasman5624]

One thing that rarely gets mentioned for SCT's but has fixed my issues in the past. Is proper corrector plate alignment first.

[@valburgess7264]

So interesting! Thank you Cole!

[@donlindgren109]

FWIW, I believe tilt and collimation are two different things addressed with two different mechanisms. Collimation with the push-pull screws and tilt with a tilt adjustor (which you may have to add to your camera). There are test jigs on KZbin that show how to test for sensor tilt and remedy it with your camera unmounted. Also, an f/2 system backspaced with starizona’s filter drawer without a filter in place will be off. No problem on an f/10 system, but is a problem at f/2. I have heard of other Nina autofocus problems and hocus-focus was updated; have you updated Nina?

[@ColeRees]

I will try out a test jig for testing camera tilt off of the scope. That's definitely something I would like to check. I am always using a filter now inside the filter drawer so backfocus should not be a problem. As for my NINA version, I'm running NINA 3.0 Nightly #23 in this video, and I just updated to #24. I always keep up to date on NINA nightly builds.

[@dumpydalekobservatory]

Hi Cole I've got a RASA 11 V1 & trying to autofocus with that is a total waste of time due to the mirror flop it suffers with, I did focus it with a mask the last session I did but I forgot to lock the mirror so as it tracked it moved & the focus went off. Dont get me wrong shooting at F2 when everything is dialled in is insane but when problems start it's a real headache lol. Hope you have got your system sorted.

[@ppoinha]

I wouldn't say focus affects stars in one side and not the other. If your tilt or collimation is off, the (focus/out of focus) could make it more evident in one side than the other but it will not contribute to fixing the underlying issue.

[@ColeRees]

Correct. One of my big issues was that it was finding “in focus” to be an incorrect AF position. This is partially due to tilt/collimation and is something I am currently working on right now. But I have found that when I use a bahtinov mask, my stars are significantly sharper edge-to-edge compared to the AF curve. This shows that my issue is only partially in collimation, but also lies in AF issues. Honestly there’s a ton of work I’ve been doing, it’ll be detailed in an upcoming video!

[@miguelsobrino7815]

I used to have problems with my Hypestar for years until I found that the camera adapter ( the one between the filter slider and the main body ) wasn't correct for my ASI camera. So I bought the right one and after that I haven't had major issues with the stars in the corners. You have to collimate the system with a star in every session. There are people who swear to tied their Hyperstar with a screwdriver and that it never changes, but I'm pretty sure that's not the case. When you begin a new session you have to check your collimation or you will have "comet like" or deform stars in the corners. It's no so time consuming, just to create a routine. And about the filters, you should add some spacer, about 0.5 to 1 mm depending on your filter's thickness. That's my 10 years experience with and Hyperstar and hope that helps to improve your images.

[@ColeRees]

Miguel, thank you for the info. One thing I can say for sure is that between all of the comments I’ve received on here and the forums online is that the hyperstar is a mixed bag of results. Funnily enough, most of the people watching my Hyperstar video already have it dialed in far batter than I ever have! I gotta be honest, I’m so thankful for all the input I’ve received. I’ve been studying collimation of Newtonian reflectors for a while so I’ve dialed in those skills and it simply does not translate to SCT Hyperstar collimation. I’ve always assumed equal coma in all directions was a product of backfocus but the consensus of youtube comments is that in the hyperstar setup, this is a problem with tilt and collimation. Anyways, I will continue to investigate and follow your tips!

[@DawgcityClev]

This is not true. You don't have to collimate every session. If so you need to replace your Hyperstar. It doesn't hurt to check, but if tightened enough you should be fine multiple sessions unless you're bashing your rig around. I've had both the 8" and now 6" Hyperstar V4's and collimate every couple months.

[@snoopy4ever]

Hello Cole !.. .I have the same OTA and Hyperstar as you ... and I got perfect stars all over the field of the camera, it is a colimation problem ... it is pretty much the same as when you collimate your SC , just got to a star .. make sure you get it out of focus..and then just use the each one of the pairs of bolts to make the perfect donut and voila!!.. I've got perfect stars all over . Hope this helps ( PS .. also I did it with the filters adapter .. so don't worry about that it will work )

[@ColeRees]

Yup, this is what I’ve been doing. They’re somewhat close to aligned right now but with a few more clear nights I’ll have it perfect. Just need some more time. I don’t have a fix for the autofocus yet though besides bhatinov plus temp comp

[@kevinburke8608]

There are Bahtinov masks for collimation of the scope (I just printed one out) It's like the regular Bahtinov mask but with more spikes. I have a hard time with it but I'm sure once I get used to it it will be easier. (harder to figure out which way to go) I use a feeler gauge and tighten the Hyperstar down to that (before I even put it on) so that the Hyperstar is starting close to perpendicular to the plate and able to push or pull on a pin. (I used to tighten all the way down intentionally and started there, but better to be able to go both directions with the screws. Feeler guage allows you to start at similar point every time and so won't start way out if i moved something) They are tricky and at times I wish I just did the RASA, but I have gotten shockingly good results. Hey, do you know if the Bahtinov mask has to be perfectly flat? My focuser went so was using the mask last night and noticed it wasn't sitting flat with one of the wires... focus seemed decent. (was using the regular Bahtinov.)

[@ColeRees]

Bahtinov masks don’t need to be perfectly flat but they should be somewhat close. They rely on multiple sets of many parallel lines, creating the three spikes when in focus. It’s becomes easier to visualize if your SCT is very far out of focus. You can see the slits go from the shape of the mask to three spikes.

[@ColeRees]

As for the tips on collimating, I will try that out! I’ve been waiting on good weather. I swapped over to f/7 for M101 so I’ve ditched hyperstar for the time being (no way am I missing out on the perfect supernova!) but as soon as that fades away I’m back to f/2.

[@kevinburke8608]

@@ColeRees That's great. I actually imaged it last night @ f2.2 because I'm having issues with guiding and I imaged the galaxy last year at the same focal length (I'll be able to do the flash back and forth thing) I wish I had imaged it @ f7 last year and this year but just couldn't. I saw a spectacular one at f7 today.

[@DavesAstrophotography]

If you are seeing a difference between Mask and autofocus, is the issue related to backlash in the focus motor and maybe need to change the overshoot steps, and try both an overshoot in or out ?

[@ColeRees]

I’ve actually done backlash compensation in all directions. My focus curve is a nice parabola. I was running a 500-step overshoot in both directions, then after monitoring it I adjusted it to 800-step overshoot OUT only, then tried it with 800-step overshoot IN only, all with extremely similar results. They all showed perfect focus at around 2000 steps higher than the “calculated final focus position” from Hocus focus. If hocus focus thinks it should be 90,000, I move to 92,000 and it’s actually in focus. I think this has to do with the hyperstar itself. HFR numbers are smaller (2.1-2.2 with autofocus compared to 2.4-2.6 with bhatoniv) but the stars are CLEARLY worse. They have a hot (and tiny) central spot with a large, diffused disk around it. Zoomed out, it’s unnoticeable. As soon as you pixel-peep, however, it’s a serious problem.

[@BruceElliott]

Hey, Cole - do you have an update for the star shapes from your Hyperstar? I just obtained the Hyperstar v4 for my club's EdgeHD 8, so I'll be going through the same process. I also got tri-Bahtinov mask to aid in collimating the Hyperstar, which I'm hoping will help. Have you tried a tri-Bahtinov mask?

[@ColeRees]

I have tried the tri-bat mask before and i can say it def helps. I have found the HoTech collimation system to be the only super-accurate way to get the collimation dialed in. I have moved away from my hyper star though, as I am using the EdgeHD for visual only at the moment. My esprit 100 has become my main imaging setup. I hope to go back and revisit the hyper star more when I finally make the move down south!

[@4sapphireb]

Does Rasa have the same issues?

[@lawrenceharris1819]

Issues? The word is problems!

[@anata5127]

Is that 0.7M Newtonian yours?

[@ColeRees]

No, I’m just in charge of operating and maintaining it! Although sometimes it feels like mine… 😂 jokes aside, it’s owned by Battle Point Astronomical Association. It’s a publicly-owned telescope! My job may be to maintain it, but anyone like yourself could become a member of BPAA and submit observation requests

[@anata5127]

@@ColeRees I see. What is location for the club? What does mean observation target? Do I suggest target, someone takes picture? Thanks