"I feel the need, the need for speed" - Hyperstar, RASA, ANY fast f ratio telescope imaging thread

[Elp]

Having started AP a few years ago when I was introduced to it by a friend (probably around 2015/2016), unbeknown to me and oblivious to the possibility of achieving such wonderous images, I began my pursuit with nothing more than an advanced digital camera (Canon G16) and a photo tripod. The first true session at a dark site with this equipment revealed the wonder of the milky way and the best image of the night (full of chromatic abberation and false colour of course) was of an arm of the milky way with a faint Andromeda visible and to top it off a meteor streaking across the image.

Since then I have been building up equipment, selling off things which didn't quite work for me and waiting to visit the dark skies again. Commitments, bad weather etc got in the way of course until I thought why don't I try from my light polluted back garden? Low and behold, things were possible to be imaged (hence why I image more than do visual), and imaged better than I thought was ever possible. So I have been eagerly trying new things, different setups, different challenges, I don't think I'm comfortable unless I'm tinkering with something or trying something new. I started this in 2021 so i've only been doing it just over a year approx. Having had an interest in many things cosmology I thought it an interesting thing to pursue.

DSO's are what primarily interest me, but generally I believe anyone can get a sense of wonder from seeing anything beyond our atmosphere.

Earlier this year I started my first full length project, NGC7023 the Iris Nebula, a difficult target but is always visible in the sky so a good one to do. Having spent 24+ hours gathering LRGB data via mono, I was happy I got some sort of result but a bit discouraged that it took so long (10+ sesssions. I've seen many people with a lot more dedication to targets). I know this hobby isn't for the impatient but lack of opportunity to image does make one wonder.

So I thought about my options. I had initially tried a 0.65x reducer with my refractor to test the faster f ratio waters. Still wanted more. Then I tried the venerable Samyang 135mm, and it's a wonder to use. But I still wanted more. RASA piqued my interest but I'd need a larger mount plus the associated costs to get the rig running. Was there anything out there that I could potentially still use with my most used mount (AZGTI?, I do have another heavier duty mount also).

Enter the Celestron C6 OTA. Then there was Starizona's Hyperstar. I have truly felt the need, the need for speed...

It's taken me a few weeks to get this working to a degree, I'm still not quite there yet as there are a few issues I still have which you can see in the following image, but managed to test out imaging on three targets in one night. I understand they won't be the best quality but I'm glad I managed to get something in a fraction of the time I would normally, I couldn't quite put a figure on it yet, a lot also depends on post processing skill but I still do this manually at the moment. An easy first target (technically the second) as it's relatively bright, a bit too bright at F2 so I imaged it at 1s and 10s subs, total time, 10 minutes, M42 The Great Orion Nebula (will add more data at some point, definitely better than my attempt a year ago):

 

So I've started this thread for any other speed runners out there running faster than "normal" setups, and also a place to discuss potential issues and solutions. There is already an excellently large Samyang 135mm thread by @Uranium235 so users of this lens please continue to post in the "Imaging with the Samyang 135mm f2" topic.

Edited October 21, 2022 by Elp

[Al_N]

The C6 Hyperstar will be on the mount a lot this winter, not that I'm expecting many clear nights with another la nina projected to last through another winter. In fact, that's why it will be mounted. I want to finish an image on that one clear night that happens every 6 weeks or so.

Here's a version of the Dark Shark I'm still trying to coax some detail out of:

1617 x 30" C6 Hyperstar, QHY183C

 

CS

Al

[Elp]

Think this is an excellent rendition of this target.

[Paul M]

Interesting build up to beautiful image. I like to call that the "classic" view. Instantly recognisable and no hint of over cooking!

It's also nice to hear it called by its Sunday Best name " The Great Orion Nebula". 👍 

I'm very interested in RASA or Hyperstar SCT's. Not sure my gradient troubled home sky would lend itself to widefield imaging though.

I'm likely to be taking the plunge one way or the other sometime soon!

[Elp]

Many thanks, just as I discovered you may surprise yourself with what's possible. The C6 with Hyperstar defaults down to 307mm focal length or thereabout and I believe the RASA 8 is 400mm so they're around the ballpark of my Z61 refractor which I don't find to be all that wide. For smaller galaxies it will image them small but I'm hoping to capture some deep fields with it at some point. The advantage of the Hyperstar route is that I can use the f6.3 reducer instead and image at 1045mm focal length, and also do planetary at 1500mm focal length its default. People say there isn't one scope which does it all but I think I might have just found it.

Regarding gradients, I too suffer from this imaging from surrounding LED lighting. Once I started using Siril's background extraction function it pretty much removed them with one button press.

Getting it running does have challenges though which I'm still going through as I'm having trouble with even flat field generation mainly and need to darken down the signal from my LED tracer panel so I can take seconds long flats (thanks to @Al_N whom has been helpful with this), I wouldn't recommend hyperstar to a beginner, but like with anything it's very satisfying once you get some sort of result.

[Fegato]

I used Hyperstar with an 8 Edge HD and now have a RASA 11. Although I've spent a lot of time sorting out the flat field with the latter, and indeed a lot of money (Octopi tilt device in particular), I feel I'm pretty close and it's really coming into its own now.  With little clear sky time, and a desire to image from home, a fast scope is a real boon.  For example - I can see we might get a couple of hours max tonight early, from 8 to maybe 10 if I'm lucky. Is it worth getting the beast out - you bet!

[Elp]

Exactly why I went down this route, I'd imagine the C8 HS8 and now the RASA 11 are of a magnitude greater due to the larger aperture.

[Elp]

So same night, as Orion drifted peacefully from view to be blocked by a building, I pointed the C6 HS6 at M45 The Pleiades and tried for just over an hour. This is my third attempt at this target but I never really gave it the time before as I was just trialling out new equipment at the time. I think with 2-3 hours more on this it'll really pop that faint nebula dust:

[ollypenrice]

I've been skeptical about the realities of super-fast systems (we all know the theory) but am falling in love with the RASA 8. It does not do everything perfectly (does anything?) but what it does, it does in spades. What I would really want to stress, though, is that this super fast system comes into its own in conjunction with a recent piece of software, StarXterminator. When you process a RASA image with StarX you can exploit the RASA's phenomenal grasp of faint signal and dodge its indifferent stellar image quality. RASA and StarXterminator is a marriage made in heaven. (Some say the same about Starnet++ but, for me, it has not done a comparable job.)

Olly

[Fegato]

54 minutes ago, ollypenrice said:

I've been skeptical about the realities of super-fast systems (we all know the theory) but am falling in love with the RASA 8. It does not do everything perfectly (does anything?) but what it does, it does in spades. What I would really want to stress, though, is that this super fast system comes into its own in conjunction with a recent piece of software, StarXterminator. When you process a RASA image with StarX you can exploit the RASA's phenomenal grasp of faint signal and dodge its indifferent stellar image quality. RASA and StarXterminator is a marriage made in heaven. (Some say the same about Starnet++ but, for me, it has not done a comparable job.)

Olly

yes, I've settled on StarXterminator as the better tool - star removal certainly feels like a necessary step in processing.

[Elp]

This is my main issue, I tend to process with the stars in so noise removal, major stretching etc is difficult and I'm always learning something new or a new technique.

I did make progress with this one, the first target of the same night. Compared to the 24 odd hours I spent with my Z61 earlier this year over 12 sessions, I did this with the HS6 in just under 2 hours. Processing plays a major factor with this target though and am sure I could process my Z61 data better if I tried again, so here it is the final target from the one night 8 odd hour marathon (clear skies for that long that's a miracle in itself):

 

Next time: work on the collimation of the lens, try alternative flat taking techniques which are proving troublesome with this.

[ollypenrice]

1 hour ago, Elp said:

This is my main issue, I tend to process with the stars in so noise removal, major stretching etc is difficult and I'm always learning something new or a new technique.

I did make progress with this one, the first target of the same night. Compared to the 24 odd hours I spent with my Z61 earlier this year over 12 sessions, I did this with the HS6 in just under 2 hours. Processing plays a major factor with this target though and am sure I could process my Z61 data better if I tried again, so here it is the final target from the one night 8 odd hour marathon (clear skies for that long that's a miracle in itself):

 

Next time: work on the collimation of the lens, try alternative flat taking techniques which are proving troublesome with this.

RASA users report the absence of dust bunnies, probably because they are too far out of focus to show. We certainly get none at all. It seems like you have a small chip so you may have insignificant vignetting. So, do you really need flats? Just a thought.

Your Iris shows only dark grey and blue colour. What has happened to the browns which ought to be there? I'd want to get to the bottom of that question.

Olly

[Elp]

The browns are there, I just reduced the background black level to make the general sky darker so the brown black separation was reduced. I also reduced the yellow early in the process. With CS2 and GIMP it's difficult getting colour selection to enable specific colour correction or bring out cloud/dust detail.

You need flats, it vignettes a lot. So these images all have bias, flats, dark flats and darks applied. I afterward also applied a manually made synthetic flat to even out the background some more.

Edited October 20, 2022 by Elp

[Fegato]

Further to my post above, I did get about 2 hours imaging yesterday evening, but a lot of subs were affected by thin clouds blowing through. I managed to get this with just 35 minutes of data (71 x 30s) - Sharpless 2-154 and  2-155 (Cave Nebula). I've pushed the stretch a lot to try and bring out everything that's going on including the dust and dark stuff. Maybe a bit much for some, but there we are. 

And yes, starless processing - couldn't have got that much stretch without it. This also allows you to grab the stars early in the stretch and protect their colours a bit (and you can saturate the colours of these separately as required). As Olly says, you won't get the best stars with a RASA, but there are ways of getting them a bit more under control.

[Elp]

That's a fantastic lot of detail for 35 minutes. I had a similar but different dew problem which effectively clouded up my subs with my last session with the Samyang 135mm detailed here, my C6 setup on the other hand was dew free, even the mount and it was right next to this:

 

[tooth_dr]

deleted

Edited October 21, 2022 by tooth_dr

[bosun21]

What is causing the multiple diffraction spikes? I know that the secondary mirror spider is responsible for them with Newtonian scopes, but why are there multiple diffraction spikes in these images taken with a hyperstar? Puzzled 🤔 

[Nik271]

The Tak Epsilon has a secondary with a spider, and no corrector plate.

[Elp]

1 hour ago, tooth_dr said:

Epsilon

How is this scope? Been considering a 130 for maybe (far) into the future. Nice colourful image.

Edited October 21, 2022 by Elp

[Elp]

1 hour ago, bosun21 said:

multiple diffraction spikes?

As with Newtonian diffraction spikes, the spikes on hyperstar depend highly on how you cable route in front of the corrector plate in the clear aperture space. I went through a few iterations of brackets until I reached version 4 (luckily I can design and print them myself), essentially you need to create an arc which the cables run behind/on top of, the best design is an almost full circle running next to the outside edge of the hyperstar up to the edge of the OTA, the subsequent diffraction becomes almost refractor like as a result. 

As I was testing this time purely for speed and what I could capture in one session I just rigged it up accordingly, as it's an uncooled camera the usb cable will cause undesirable effects but the spikes weren't as bad as I was expecting and the camera performed well considering its not designed for dso:

With the cooled camera the 12v cooling cable and usb cable come out the back of the camera and can be tied down to the body with elastic bands so they're hidden/occluded behind the base flange of the hyperstar lens, and then run each cable down the custom routing bracket (v3) which you can see in the top of the image. 

I may well post pics of various designs of bracket and their diffraction patterns in the near future for reference.

Edited October 21, 2022 by Elp

[tooth_dr]

1 hour ago, bosun21 said:

What is causing the multiple diffraction spikes? I know that the secondary mirror spider is responsible for them with Newtonian scopes, but why are there multiple diffraction spikes in these images taken with a hyperstar? Puzzled 🤔 

I’ve deleted my post. Didn’t realise this was a thread for only RASA and hyperstar systems. 

[bosun21]

41 minutes ago, Nik271 said:

The Tak Epsilon has a secondary with a spider, and no corrector plate.

I’m referring to the images taken with the C6

[Elp]

19 minutes ago, tooth_dr said:

I’ve deleted my post. Didn’t realise this was a thread for only RASA and hyperstar systems. 

It's not, any fast telescope systems welcome. I've edited the title to include ANY.

[tooth_dr]

On 21/10/2022 at 20:48, Elp said:

It's not, any fast telescope systems welcome. I've edited the title to include ANY.

2 hours 55 minutes in 3.5nm Ha on the Epsilon F2.8, taking during the middle of July (!)

You were asking about recommendations - I think it's a fantastic scope, but I ended up replacing the focuser as the stock one wasnt good.  I bought the scope used so that may have been the reason for the bad focuser.  Not sure I would spend the money on a new one, hard to say as they are very expensive.

 

[Elp]

Lots of details there, it's great what ha imaging reveals.