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

[tooth_dr]

13 hours ago, Elp said:

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

The Sadr region even surprised me, so much going on. 

[Elp]

Was delighted to have a clear night yesterday so decided to setup the hyperstar again, was going to try to do a mosaic this time but low and behold, clouds rolled in after an hour and stayed so couldn't. Had to throw half the subs away so pretty much the result of an hours imaging.

Thanks to @HollyHound for selling me their 294MC uncooled, thought it was going to be troublesome but managed to take 7.5s flats with my LED tracer panel dimmed down right to the lowest setting with two opal perspex/acrylic sheets and one dark grey transparent perspex/acrylic sheet, seemed to dim down far enough. Still didn't calibrate out properly so I also applied a synthetic flat to it which worked. The 294MC shouldn't work with the hyperstar 6 as its max diagonal size of illumination is 16mm, the 294MC is 23.2mm diagonal, was suprised it worked so well. Should have not sampled properly either but again surprised with the result, overcooked but I like the vibrance of the heart, and now the soul still burns...:

(On another note, someone pointed out to me it looks like someone looking sideways, now I can't stop seeing Alfred Hitchcock/Winston Churchill).

[Elp]

An alternative, first time Starnet actually worked as most of the time I process with stars in the image. Quite like the rosy look.

[Elp]

Did another session over the weekend with the 294MC and tried 3 targets in one 8 hour session, alas I think im getting the 294 flats issue so had to abandon processing of two of the targets, one of which was a reflection nebula on a moonlit night so was fighting against all odds anyway. I like how this one turned out however, following on from the Heart a few weeks ago:

[Elp]

Its been a while (I've been using other setups).

Whilst doing another project I decided to end the run with a 1 hour session imaging the brightening (probably at its limit now) comet C/2022 E3 ZTF. Never imaged a comet before but the GEM28 tracked like a champ, from start the finish the stars hardly moved, I don't think they did for the whole hour. Also a test for the HS, imaging directly above LED lights so I was limited to 20 second exposures, would have loved to get the fainter tail of the comet, the system however caused a bright highlight in front of the comet, rather than remove it I left it in as it is a strange shaped comet with its coma pattern.

The real challenge this time was processing it, took a few tries but at the same time I was trying to standardise a pre process routine to get the best calibration done, still learning on this as each setup I use produces different results. In the end I used Siril rather than DSS.

So, here it is, the last seen 50,000 years ago and likely will never be seen by humans again comet C/2022 E3 ZTF.

[Elp]

RGB imaging I've always had an issue with due to LP gradients, so in the meantime I've tried to standardise a process for lights calibration. During this time I decided to try something which I probably shouldn't being in a bortle 7, M78 the dark nebula near Orion's Belt.

I decided to keep this one starless and generally the colour as the camera saw it, I like that it looks like a Turner or a Baroque painting from the old masters. The composition I believe turned out well too as it makes your eyes move around it and draw towards the bright highlighted centres then back out again (to me anyway).

[JeremyS]

Looks atmospheric and moody 👍🏻

[CCD-Freak]

M45 from the Okie-Tex Star Party 

Sharpstar 150mm F2.8 Hyper Newt with a ASI533MC through a Baader UV-IR filter.   75 x 1 minute captured and processed with AstroArt.

Edited January 30, 2023 by CCD-Freak

[Elp]

 

6 hours ago, CCD-Freak said:

Sharpstar 150mm F2.8 Hyper Newt

Great nebulosity, how is the sharpstar 150mm to use? Looks like a neat scope.

[CCD-Freak]

On 30/01/2023 at 04:29, Elp said:

 

Great nebulosity, how is the sharpstar 150mm to use? Looks like a neat scope.

I have really enjoyed the SS15028HNT.  Imaging at F2.8 is a joy.   I had to do a bit of tweaking when I first got it to fix some movement of the primary mirror but once that was solved it has played well.  I have mainly used it with an ASI533MC and a recently acquired ASI2600MC. 

NGC7023 the Iris Nebula   300 x 120s (10 hours total)  ASI533MC with a Baader UV-IR filter riding on an AP900 mount at my SRO dark site.   Captured and processed with Astroart 8.

 

[Adam J]

On 20/10/2022 at 18:56, ollypenrice said:

It does not do everything perfectly (does anything?) but what it does, it does in spades.

So what are its deficiencies in your opinion as a RASA owner?

I have been taking note of RASA images and my possibly controversial opinion is that they can seem to lack in terms of resolved detain in brighter targets. I guess the poor stellar performance is a more directly visible symptom of this.

What I mean by that is that when I see RASA images of bright targets such as the North America Nebula (as one example), I tend to think that they appear soft in comparison to images by similar focal length refactors at or about F5.

This is something that I would anticipate from examining the published spot diagrams for a RASA. But its probably also caused by the fact that RASA imaging leans towards OSC cameras for various reasons and so the softer optics are combined with the lower sampling of an OSC (most so in red) to limit the resolved detail. 

Now this is only the case for bright targets when both the F2 RASA and the F5 refactor can achieve a suitably high signal to noise ratio within a reasonable amount of time. 

When the RASA of course wins is when imaging time is very limited or when the target is very dim. As in these cases the signal to noise ratio of a slower system will be the limiting factor in terms of resolved detail or in the extreme case the very ability to detect the presence of the object at all. 

As a side note, I think this is a reasonably advanced topic to be found in the getting started with imaging section. Unless we are advocating a RASA or a Hyperbolic Newtonian a starter scope. 

 

Adam 

 

 

Edited February 2, 2023 by Adam J

[ollypenrice]

1 hour ago, Adam J said:

So what are its deficiencies in your opinion as a RASA owner?

I have been taking note of RASA images and my possibly controversial opinion is that they can seem to lack in terms of resolved detain in brighter targets. I guess the poor stellar performance is a more directly visible symptom of this.

What I mean by that is that when I see RASA images of bright targets such as the North America Nebula (as one example), I tend to think that they appear soft in comparison to images by similar focal length refactors at or about F5.

This is something that I would anticipate from examining the published spot diagrams for a RASA. But its probably also caused by the fact that RASA imaging leans towards OSC cameras for various reasons and so the softer optics are combined with the lower sampling of an OSC (most so in red) to limit the resolved detail. 

Now this is only the case for bright targets when both the F2 RASA and the F5 refactor can achieve a suitably high signal to noise ratio within a reasonable amount of time. 

When the RASA of course wins is when imaging time is very limited or when the target is very dim. As in these cases the signal to noise ratio of a slower system will be the limiting factor in terms of resolved detail or in the extreme case the very ability to detect the presence of the object at all. 

As a side note, I think this is a reasonably advanced topic to be found in the getting started with imaging section. Unless we are advocating a RASA or a Hyperbolic Newtonian a starter scope. 

 

Adam 

 

 

Strictly speaking I'm a RASA user, not an owner, and my detailed findings were published in Astronomy Now in a full length review. If you want the best possible star shapes with the highest degree of consistency then buy a high spec refractor. I don't think that's very controversial except, perhaps, among those who don't think star spikes are artifacts. 👹 

Modern processing, involving the separate stretching of stars and target (where they are not the same) means that the need for the best possible stars at capture is greatly diminished. The RASAs are widefield instruments by dint of their focal lengths, so we are talking, most of the time, about a large number of small stars. The stars we are getting in this context, processed through StarXt, are OK. The non-stellar parts of our captures are sensational - in my view. It's hard for me to make direct comparisons between the dual Tak FSQ106 rig we ran and the single RASA because we are using a modern CMOS in the RASA as opposed to old CCD in the Taks. What I will say, without any doubt, is that I would not go back to the old dual rig over the RASA at any price.

I'm not a pixel peeper and I don't process for pixel peepers. I'm interested in the big picture, seen at a size which keeps it the big picture. If that's your thing, you'll love the RASA. If you look at images in a different way it may not be.

Olly

[gorann]

4 hours ago, Adam J said:

So what are its deficiencies in your opinion as a RASA owner?

I have been taking note of RASA images and my possibly controversial opinion is that they can seem to lack in terms of resolved detain in brighter targets. I guess the poor stellar performance is a more directly visible symptom of this.

What I mean by that is that when I see RASA images of bright targets such as the North America Nebula (as one example), I tend to think that they appear soft in comparison to images by similar focal length refactors at or about F5.

This is something that I would anticipate from examining the published spot diagrams for a RASA. But its probably also caused by the fact that RASA imaging leans towards OSC cameras for various reasons and so the softer optics are combined with the lower sampling of an OSC (most so in red) to limit the resolved detail. 

Now this is only the case for bright targets when both the F2 RASA and the F5 refactor can achieve a suitably high signal to noise ratio within a reasonable amount of time. 

When the RASA of course wins is when imaging time is very limited or when the target is very dim. As in these cases the signal to noise ratio of a slower system will be the limiting factor in terms of resolved detail or in the extreme case the very ability to detect the presence of the object at all. 

As a side note, I think this is a reasonably advanced topic to be found in the getting started with imaging section. Unless we are advocating a RASA or a Hyperbolic Newtonian a starter scope. 

 

Adam 

 

 

I can agree that star shape is not the strong side of RASAs, but it is their light grasp and what they can achieve, especially if you run them for 10, 20 or 30 hours. Then they will see things that no refractor has ever seen. They just go so much deeper and that is what excites me about them. If you have an OSC or a mono at the end of them does not to seem to make a big difference. Here is an example where I by chance realized that there is a big SNR just next to the Heart Nebula:

https://www.astrobin.com/6zp16s/?

 

Edited February 2, 2023 by gorann

[tomato]

Is it indeed just a case of horses for courses? If widefield, dim objects are your thing, fast optics are the way to go, if capturing smaller, brighter targets in more detail is what you are after, go for the longer FL scope. 
For example with the RASA, I can get a nice 2 panel image of the Spaghetti Nebula in one sitting, but I don’t have the resolve to try the same target with an F7 refractor, the UK weather would wear me down.

[Elp]

Doesn't the central obstruction have a bearing with regard to the "softness"? I would put some doubt on this as Newtonians are usually sharp.

My HSC6 will never match my Z61 for sharpness but that's not the point of it, I bought the HS for speed considering the frequency of bad weather, the aperture increase also aids this. I also use a SY135mm for the same reason for speed of capture.

If I want, I can also image some small stuff at F6.3, but I think that will test my patience after experiencing this change.

Edited February 2, 2023 by Elp

[Adam J]

3 hours ago, gorann said:

I can agree that star shape is not the strong side of RASAs, but it is their light grasp and what they can achieve, especially if you run them for 10, 20 or 30 hours. Then they will see things that no refractor has ever seen. They just go so much deeper and that is what excites me about them. If you have an OSC or a mono at the end of them does not to seem to make a big difference. Here is an example where I by chance realized that there is a big SNR just next to the Heart Nebula:

https://www.astrobin.com/6zp16s/?

 

Gorann of course I have already seen this fantastic image and commented on it at the time. Along with many other examples of your work with the RASA. But I would essentially say this is in line with my comments. In that it's an excellent tool for going after very faint structures. 

What we do see here is a very faint structure in terms of the SN reminant next to a very bright object in the form of the fish head / heart in the linked image. 

Adam 

[gorann]

Actually, I have lately experienced that the cosmetic problem with star shapes in RASAs  can in most cases easily be fixed with a dose of BlurXT on the linear unstretched image.

[ollypenrice]

11 hours ago, Elp said:

Doesn't the central obstruction have a bearing with regard to the "softness"? I would put some doubt on this as Newtonians are usually sharp.

My HSC6 will never match my Z61 for sharpness but that's not the point of it, I bought the HS for speed considering the frequency of bad weather, the aperture increase also aids this. I also use a SY135mm for the same reason for speed of capture.

If I want, I can also image some small stuff at F6.3, but I think that will test my patience after experiencing this change.

In truth, I don't think the RASA is 'soft,' exactly.  Stars present a very specific optical challenge and it is on stellar shapes that it is at its weakest. In terms of the resolution of other detail, I've no beef with it - though I haven't done a direct comparison.

To endorse the points made by Goran and Tomato, a difference in speed at the scale offered by the RASA doesn't just make a convenient difference in time, it makes, in reality, the difference between the possible and the impossible. I have participated in a 400 hour mosaic once, with Tom O'Donoghue. On occasion we had three identical rigs running simultaneously. I probably wouldn't do so again, but shooting 400 hours in 90 hours is a very different proposition and that's what we did for the M45 to California mosaic in the RASA.

Olly

[Fegato]

13 hours ago, tomato said:

Is it indeed just a case of horses for courses? If widefield, dim objects are your thing, fast optics are the way to go, if capturing smaller, brighter targets in more detail is what you are after, go for the longer FL scope. 
For example with the RASA, I can get a nice 2 panel image of the Spaghetti Nebula in one sitting, but I don’t have the resolve to try the same target with an F7 refractor, the UK weather would wear me down.

Yes exactly.  What I really want is to complement my RASA here with a longer FL refractor at one of the remote hosting sites in Spain…. I just need to find the right moment to suggest this is a good idea to my wife!

[Elp]

Whilst I'm in the process of doing a long(er) project, I decided as some Summer targets are within reach, whether it was possible to image them from my home location. So I moved the scope to another position and tried the HS6 on M16, one I've done before but off site, never thought I could do it from where I am but it's quick enough to be able to do in 1-1.5 hour segments, so looking for feedback really (is this normal/expected/not enough (I know it needs a lot more total time)), this is 30 minutes only using an Lextreme and 294mc uncooled, slight post processing, NR and crop:

 

Previous narrowband effort (also short time), different setup:

[Elp]

Another one finally done:

 

[Elp]

Just a rudimentary test of the C6HS6 after my targets had set for the night (maybe a preview of what the Origin might do?), I wanted to try the Live (EAA) mode in the asiair, 30s exposures x 30 so 15 minutes total from a Bortle 7, Optolong Luminence filter with a 533MC Pro. Stars are odd shapes, I'll have to compare this to my DSO images done on the same night. Tried to process the same, first image is the stacked air image (no calibration files, colour calibration, histogram stretches, levels and slight contrast adjustment in PS), second image is the individual files processed in Siril (AP workflow, calibrated, registered, stacked without rejection, background extraction, colour calibration, histogram stetches, very slight levels and contrast adjustment in PS). Not exactly a fair comparison as the calibration files and background extraction makes all the difference, but a comparison between basic EAA without calibration (F2 really needs it to remove the vignetting) and DSO workflow:

Asiair Live mode stacked no calibration files (15 min total):

 

AP workflow stacked (same data):

[Elp]

Another comet imaged (12P/Pons-Brooks), I need to see how this comes out via a refractor for comparison:

 

[Elp]

Recently added this into the narrowband imaging challenge, short total time but I'm happy I got some extended gas regions so likely I'll keep adding to this every season, when I do it properly I'll add in RGB refractor stars, and yes there is S2 signal in the target concentrated mainly in the bottom of one of the "arms" where it connects to the "head" even after only an hour or so of capture:

[Elp]

Another day, another target. NGC2237 Rosette Nebula in SHO. I'm not done with this one quite yet, also submitted to 2024's narrowband competition: