Struggling with Hyperstar

[Stinky_Pete]

I picked up a second hand hyperstar to go with my C6 and im struggling to get good results with it. It originally came with the incorrect adaptor for my camera (294 pro) and Dean at starzona has been a great help getting a new one out to me. Trying it out last night on M42 (Bortle 5-6 skies but some high cloud) i have to say im underwhelmed with what i achieved. Im not sure if its me, the conditions or the equipment. This is 30 subs of 30 seconds each, focused with a Bahtinov mask, no flats or darks as i was only playing about. The second image is 1 min subs x30 from my 200mm Newt at F5 just with a modded dslr from 5 years ago. I seem to have oval shaped stars so tracking is a bit off although i know that my pier has been drift aligned recently and the whole thing is sitting on a tuned Neq6 with a guided RMS of >1 usually. Other issues i am still getting is a slight v shape to the stars in the corner but the chip in the 294 is quite large so I'm not that surprised with that (the image can be cropped anyway). I cant really see any improvement in "depth" even tho im running at F1.9 instead of F5 at comparable exposure times and number of subs. Am i asking too much of the system? it was a frustrating and tiring night and my expectations could be too high for sure but i was hoping to have a much more convenient setup so i can get out much more easily when there is a gap in my frenetic life 

any tips gratefully received.

[michael8554]

To eliminate PA, guiding, and stacking artefacts, you should only examine a single stretched short exposure, as short as possible.

Michael

[Stinky_Pete]

ok below we have an untouched frame direct from DSS which i used to convert from fits to tiff then 8bit jpeg for size constraints. The other one is the same sub but cropped and a simple stretch, stars are still elongated and v shaped at the edge of the frame. 

[michael8554]

On your single sub I see equal amounts of coma in all four corners, as you suggested.

All stars are elongated roughly top Left to Bottom Right, as you suggested, but which I think is an RA error, not a Dec PA error?

I don't believe anyone says HyperStar is easy, in fact most advice is to steer clear unless you are a perfectionist in setup.

Michael

[Stinky_Pete]

im surprised if its RA error over that length of sub (30s) or my guiding in my other setup would be very biased, the image would move out of frame over the length of an evenings imaging .whats the best way of checking that?...unless sidereal rate is off on the stellarmate? 

Edited March 21, 2021 by Stinky_Pete

[michael8554]

You mention the NEQ6 is guided, so is your RA error twice your Dec error  in PHD2 ?

How good is your PE ? 30 seconds would be halfway to the peak of the mount's Periodic Error, if it's a 4 minute worm ?

Michael

[Stinky_Pete]

Not guided for these images I'll.have to check my graphs next time it is clear and im using my newt setup. 

[AMcD]

The Hyperstar promises a great deal but to extract from it its full potential is difficult and regularly frustrating.  I have certainly not yet achieved it with my C8 and regularly get to the point of listing it on UK Astronomy Buy & Sell, only to relent when I think I have found some new way of making it work.  Particular difficulties include the very uneven field illumination, the fact that it is intolerant of anything but perfect alignment with the telescope's optics and the fact that the Hyperstar itself needs careful collimation.   I found this article on Cloudy Nights (and the comments underneath it) helped me identify the particular areas that need a lot of attention to get it to work to its full potential (The Amazing HyperStar: A Guide to Optimize Performance - Articles - Articles - Articles - Cloudy Nights).   I do feel your pain.  I am currently in a period of being determined to get it to work but give it a few weeks and I may be back to composing that advert for UK Astronomy Buy & Sell 😄

[kirkster501]

I hope you get it working, it can be so frustrating at times.

Personally, I feel Hyperstar is a way for Celestron to tick the box to say "DSO imaging capable".  Sounds cynical but that's my view personally.  Hats off to people who like it, can get focus at F2 and maintain it and get good results.  If you have clear nights every night and have multiple nights to play around collimating two optical systems and can perfect it then great.  But in the UK we do not and we need simpler AP solutions to make the most of precious few opportunities.   None of that helps you of course and I do hope you get to the bottom of your issues.

Edited March 23, 2021 by kirkster501