jjosefsen

"LOUSY NIGHTS" 🤣

Hmm ok, try this one:

https://discord.gg/nighttime-imaging

https://discord.gg/rWRbVbw

This should work..

This has certainly been an interesting and educational read, so thank you for that.

I don't think you can say that synthetic bias works for all flats < 5 sec. I have an ASI1600 clone and I have amp glow in 1,8s darkflats.. 🤔

So it is also equipment specific.

1 hour ago, vlaiv said:

Main difference is in two things:

1. speed of capture

2. absence of microlens artifacts

Speed of capture - this comes in two distinct "flavors":

1a - higher QE. We can say that ASI2600 has up to 50% higher QE than ASI1600

In 10 hours with ASI2600 - you'll collect as much signal as in 15h with ASI1600

1b - size of sensor - this is not something that you should really consider because you won't be changing your scopes, but larger sensor is faster sensor because it can be paired with bigger scope.

In fact - this is something that you might find interesting with your C11 - when you bin x2 or x3 - you get small pixel count in final image with ASI1600. Bin x3 will give you image that is about 1600x1200 if I'm not mistaken. With ASI2600 - you'll get larger image with same bin factor

Second point is self explanatory.

You say that speed is not that important - then it is really down to microlens - would you spend your money to get rid of them.

Isn't the IMX571 in the 2600 also a much "cleaner" sensor than the, at times "finicky" panasonic sensor in the 1600?

I have seen a few raw frame examples, and they look super smooth!! I know there are many factors playing in here..

I wanted to come back here and let you know how I am getting on with the RC now that I finally had a clear night to test, albeit under a 100% illuminated moon.

This is a quick 2 panel Ha image of NGC 7822 aka Sharpless 2-171, with almost 2 hours on each panel, and as mentioned under a full moon.

Quick and dirty process with a bit of Deconvolution, Noise reduction and a stretch.

In the end I didn't  quite go all the way as @davies07 suggested, and remove the secondary mirror and use the disc method.

I collimated using the REEGO Pro and MoR module, but the information you provided gave me the understanding of what was going on, and what I needed to fix.

This was particularly helpful as TS Italia has still not released a manual of how to use the MoR, but basically the same principles as your fine documentation.

I didn't even fine tune on a star for this image, so there is maybe still a little room for improvement, but I was desperate for some data after months of clouds.

Again thank you for the assistance, it was/is much appreciated!

//Clear skies, Johannes

On 20/12/2021 at 18:13, James Ritson said:

Aha, not too far away then I take it? I used to live in Woodhall Spa, moved to Newark, then to Boughton (near Ollerton) which had some great skies for seeing around the pit wood, then finally moved back to Newark this year.

Hi, the deconvolution would certainly be useful. May I ask what local histogram equalisation does? Is it similar to the tone stretching macros in my macro pack? (They will perform various nonlinear transforms such as log2, sqrt then do histogram equalisation).

Frame weighting: is that evaluating the quality of frames? Photo has the "Select best light frames" percentage option when stacking which might be useful?

I did also read somewhere—I can't remember whether it was here or another forum—that someone passed on using Photo because the stacking did not offer kappa sigma clipping. This confused me because it's the default option in Photo and is pretty much essential for removing outlier hot pixels and inconsistent pixels.

I can't say whether any new features will make it into the next version, as the dev team are all hard at work and need to focus on other longstanding features that have not yet been implemented. We did talk about the possibility of guided star removal in the future, however.

I won't even try to explain the math (I can't  ), but you can use it to enhance contrast on variable structure sizes in a non-linear image.

From the documentation:

Histogram equalization takes the histogram and computes a transfer curve, which grants more brightness range to higher histogram peaks and less brightness range to histogram valleys. In other words, large areas of similar brightness get more contrast. Local histogram equalization works on individual pixels and computes a transfer curve from the histogram of a pixel neighborhood.

"Select best light frames" is nice, but what is it based on? PSF? SNR? It would be nice to have a little more input on how it determines the best frames.

Even better would be if the weighting would be taken into account when stacking, so not just rejecting whole subs, but using all (above  a threshold) and just varying the contribution to the stack.

I understand that the above is some very specific Astro related things, and you are getting into the nutty gritty part of it, so maybe not at the front of the roadmap.

Like I said I really enjoy Affinity Photo, and it is a Photoshop slayer for me, which speaks for its great use and value.

I hope we hear more from you on this forum, particularly about your own imaging projects as well. 

//Clear skies

Hi james,

Great to see you here!

I really like Affinity Photo and have been playing with it in place of using PixInsight, as I enjoy working in it.

I still feel like there are some things in PI I can't really do without: Deconvolution and Local Histogram Equalization for instance, and also some more control on the stacking process, particularly when it comes to frame weighting.

So for now it is still a combination of PI and Affinity Photo for me.

Can you tell us if there are any planned new features related to Astrophotography comming in the next year?

I loved everything about this, from the large mosaics to the deep HOO.

I have heard multiple people complain that the new 5V version of the EAF doesn't work well in the cold.

Is this perhaps the 5V version?

17 minutes ago, Adreneline said:

Thank you - the RedCat+1600 and Samyang+183 is a win-win combination.

I can do a little more "pop"  

I was going to do a lot more "pop" but thought better of it  

Thanks again for your kind comments.

Adrian

Brilliant!

Quick question regarding the Redcat.. If I remember it had some QA issues in the beginning, is this still an issue or have subsequent batches been better?

Very nice image! The details are really crisp!

Personally I don't mind the more subtle colors, but it could also look good with a little more "pop" maybe.

Good job! Star colors look really nice.

Some of the large stars are a little bloated, maybe seeing was not the greatest?

The HOO is very nice.

I really don't like green in astro images so the SHO version is out for me, I would have shifted  the colors in post to avoid the green.

My guess is you are trying to load a template and not a sequence. 

The heated window is on all the time I believe. The USB traffic setting is to adjust how fast data is pushed over USB. If you don't have issues just leave it and forget about it.

You can do a PA routine similar to that of the iPolar (plate solved PA) using your guidescope and camera and PHD2, which would let you ditch the windows pc.

In terms of why it is differing, are there perhaps any location settings that are off somewhere? Either mount (INDI/ASCOM) or in the iPolar application?

That is almost the only thing I can think of.

Wow that is "baller" as the kids say! 👏  Very very nice.

I hope it all turns out OK for you and everything works.

46 minutes ago, Clarkey said:

I followed the really good advice from David when I was trying to collimate my RC8. I have developed my own method (albeit very similar to that described by David but using the REEGO (TSRCKOLLI). Follow the guidance carefully and you will get there. It is worth the effort as the RC's are excellent for AP.

I have the REEGO and their new reflector module MoR.

On 26/11/2021 at 11:44, FLO said:

@jjosefsen  Was your RC6 purchased from us?  

If yes then we'll happily put it on the optical bench and check it for you. 

No, this is a second hand scope I found locally.

Unfortunately my favourite astro shop (you) is suddenly very far away due to taxes and stuff. 🥺

On 26/11/2021 at 11:37, davies07 said:

Yes, sorry, Steve. Here goes:

I think the OP has two problems: his RC6 is out of collimation and there seems to be significant tilt between the pointing of the primary mirror and the optical train. It will not be possible to properly collimate the scope with any device that is inserted into the focuser. Any attempt to correct the tilt due to the misalignment will result in a scope with what I term "squinted collimation": the mirrors will be parallel (at best) but the optical axes of the mirrors will not be aligned. The way to proceed is to remove the optical train completely and collimate the primary and secondary mirrors on their own on the bench as described here:

https://www.dropbox.com/s/avpu2vn6s3ynsz5/Collimating GSO Ritchey Chretien with a plastic disc V2.pdf?dl=0

These notes deal with the RC8 but there is an article on the specific collimation of the RC6 in this issue of my club newsletter:

https://www.dropbox.com/s/ni0n7yvsfrwis40/September 2020 Newsletter.pdf?dl=0

Once close collimation of the primary and secondary mirrors has been achieved on the bench, it remains to test the scope on a star test to eliminate any residual coma. This should be done on a star in the centre of the field of view. The scope should be just a smidge out of focus 'out' not a huge doughnut. Here is an image from a star test on my RC8.

The focuser is around 100 counts (0.25 mm) out of focus out. The blue lines are part of the centre mark on the N.I.N.A. image viewer. Note the central Poison spot. I adjust the primary mirror to get the Poison spot central. The required adjustments to the primary should be very slight indeed.

The secondary should not be adjusted at this stage. Check the symmetry of how the stars look in the corners. They should look the same in each corner. 

The methods I've described are due to Es Reid, by the way. The method I've described is based on the techniques he uses in his commercial work. 

As to the misalignment of the optical train with the primary mirror: I think this is a common problem with the GSO designed RC6 and RC8. On my RC8, the primary mirror is secured to the primary support structure with a ring clamp and an O-ring between the clamp and the glass.

I had a huge misalignment on my RC8 and I found it to be due to a perished O-ring, so I replaced it. To inspect the O-ring does need you to dismantle the primary mirror from its holder but its not a difficult job if done with care. While you have the primary mirror in your hand, you could paint the edge with black acrylic paint (Warhammer Chaos Black worked well) to hide the rough edge of the glass and the marks of the clamp that held the mirror while it was silvered. Doing this will really tidy up the halo around your star images.

Do not over-tighten the ring clamp. You'll stress the mirror.

Finally, you can use the tilt focuser to remove any remaining tilt between the focuser and the secondary. I do have a bit of residual tilt on my scope but I don't correct for it. My images seem fine without it.

By the way, if I put a laser on my scope it says it is out of collimation!! 

Sorry for my reticence in posting on the open forum, but I've said all this (mostly) before but forums seem to have short memories. The information is here if people would search for it.

 

David

 

 

Thank you so much for this, very well written information, it is a very interesting read.

I am currently visiting family and I only have my phone, so will take another look at this when I get home to my PC.

I really hope I can get this thing working well, as I plan to upgrade it to an 8" version at some point, maybe when I finally get around to building an observatory.

Hi,

I just bought a Star Adventurer 2i and a brand new Canon EF 50mm 1.8, and while testing it this problem reared its ugly head.

My DSLR has been in storage for a couple of years, but I can't see why it would suddenly have this problem, so I am hoping it is the lens.

4s exposure, ISO 1600 at F3.5

Can any of you tell if this is likely the lens or the camera?

I am a bit of a novice when it comes to DSLR's and lenses... :S

Edit: I don't have any other lenses for this camera, and I can't think of any of my buddies with EF lenses..

So I had some real progress last night..

Having aligned the focuser to the secondary yielded the best stars I have had to date on this thing..

So the optical axis between the primary and secondary mirror is quite a bit out of alignment right now, but apparently having alignment between the focuser and secondary is "more important". That is a bit of simplification obviously, but seems correct in my instance.

I have ordered a tilt plate adapter for M90 connection, this will allow me to align the primary to the secondary again, and then use the tilt plate to align the focuser.

Hopefully this will sort things out.

With the reducer in the imaging train, my focus point is quite close to the scope, I don't have to extend the focuser much, so I think I can get away with the stock focuser for now. But upgrading that will definitely be on the todo list if I can get this thing humming to my liking.

I also fine tuned the distance between the mirrors further, and it was a massive improvement to focus and led to much tighter stars across the entire field.

3 hours ago, Adreneline said:

I'm not sure I totally understand the question, however, it is possible to compensate for out of parallel / not orthogonal because the Baader has a built in tilt adjustment. I am pleased - very pleased! - I have not had to use this feature.

Apologies if I have misunderstood your question.

Adrian

No that was exactly what I was trying to ask  So thanks.