A radical departure for me...

[tomato]

Looking good!

And a departure from Atik’s Artemis capture software? A lot of change happening at once.

I got my RASA/OSC combo up and running with NINA, with no drama.

[ollypenrice]

1 hour ago, tomato said:

Looking good!

And a departure from Atik’s Artemis capture software? A lot of change happening at once.

I got my RASA/OSC combo up and running with NINA, with no drama.

Yes, I dread moving away from Artemis Capture (which I call Artemis Rapture ) but Atik have moved away from it themselves. I gather their new software isn't even written on papyrus.

I ask you!

Olly

[gorann]

Looks great Olly! Nice to see a RASA bathing in sunshine!

The first thing you need to remove before you attach a camera is that front glass on the lens assembly.... Never understood why they have it there, maybe just for protection

[nfotis]

I guess that you know it already, many RASA users curve the camera cables in order to avoid diffraction effects:

https://www.cloudynights.com/topic/681476-diffraction-minimizing-wiring-loom-for-rasahyperstar/

Best luck in your experiment.

N.F.

 

[ollypenrice]

5 hours ago, nfotis said:

I guess that you know it already, many RASA users curve the camera cables in order to avoid diffraction effects:

https://www.cloudynights.com/topic/681476-diffraction-minimizing-wiring-loom-for-rasahyperstar/

Best luck in your experiment.

N.F.

 

Yes, I had a thorough explanation of curved vane diffraction from an optical engineer who comes here regularly. We'll go for the semi-circle and won't run the guidescope to the camera hub because it's an extra cable in front of the corrector for nothing.

Camera and focus motor are now ordered.

Olly

[tomato]

In my experience the Celestron RASA focus motor is a great bit of kit, easy to install and precise operation. I know Gorann’s experience is the focus doesn’t shift very much at all on these scopes but great to be able to check without getting hands on.

[ollypenrice]

45 minutes ago, tomato said:

In my experience the Celestron RASA focus motor is a great bit of kit, easy to install and precise operation. I know Gorann’s experience is the focus doesn’t shift very much at all on these scopes but great to be able to check without getting hands on.

Paul's ordered one so your endorsement is welcome! Thanks,

Olly

[gorann]

If it is going to be fully automated then a focus motor is of course necessary, but as mentioned the RASA8 holds focus very well, which is surprising for an f/2 scope, and I never had to refocus during a night.

It is very easy to organize the camera cables by taping them to a circular piece of steel wire, and let them out in the slit of an Astrozap dew shield (or similar). A dew heater is not needed - the camera seems to produce enough heat.

Edited July 6, 2021 by gorann

[ollypenrice]

3 hours ago, gorann said:

If it is going to be fully automated then a focus motor is of course necessary, but as mentioned the RASA8 holds focus very well, which is surprising for an f/2 scope, and I never had to refocus during a night.

It is very easy to organize the camera cables by taping them to a circular piece of steel wire, and let them out in the slit of an Astrozap dew shield (or similar). A dew heater is not needed - the camera seems to produce enough heat.

 

 

Maybe it's not just the heat: the stirring of the air by the fan probably helps as well? But it's great to hear that dewing isn't a problem.

Your cable loops from the camera are some distance from the corrector. I was going to run ours down the camera side and then in front of the corrector so as to be as far out of focus as possible but perhaps this isn't necessary.

Olly

[wimvb]

12 minutes ago, ollypenrice said:

Maybe it's not just the heat: the stirring of the air by the fan probably helps as well?

My thought also. You wouldn’t want much heat coming from the camera, because that would create problems of its own.

I don’t think it matters much where you have the cables crossing the light path. The distance from the back of the camera to the corrector plate can’t be more than about 15 - 20 cm.

On the other hand, there is more diffraction from the full loop in Göran’s setup as compared to a half loop, since it is every edge that contributes to diffraction. Whether this will be noticable in the images is another matter.

Edited July 6, 2021 by wimvb

[tomato]

Olly, Just another observation on the camera cooling which may be relevant given the climate at your location.

On milder nights (10+ deg ambient temp) I found that with the dewshield in place my QHY 268 cooling could not maintain my set point temp of -20 deg. This was definitely due to the warm exhaust air from the camera being recirculated within the confines of the dewshield, as soon as I removed the shield the camera ran at the set point with around 65% of the cooling capacity utilised. No problem with the dewshield in place on cold nights.

To be fair, -20 was probably in excess of what was required, but the cameras are obviously not designed to pull in their heated fan exhaust.

If you are using decent quality power and USB cables you might find it a struggle to route them down closer to the corrector plate, I use Gorann’s arrangement with no (to my eye at least) unpleasant diffraction artefacts.

[ollypenrice]

1 hour ago, tomato said:

Olly, Just another observation on the camera cooling which may be relevant given the climate at your location.

On milder nights (10+ deg ambient temp) I found that with the dewshield in place my QHY 268 cooling could not maintain my set point temp of -20 deg. This was definitely due to the warm exhaust air from the camera being recirculated within the confines of the dewshield, as soon as I removed the shield the camera ran at the set point with around 65% of the cooling capacity utilised. No problem with the dewshield in place on cold nights.

To be fair, -20 was probably in excess of what was required, but the cameras are obviously not designed to pull in their heated fan exhaust.

If you are using decent quality power and USB cables you might find it a struggle to route them down closer to the corrector plate, I use Gorann’s arrangement with no (to my eye at least) unpleasant diffraction artefacts.

More good info. Thanks. I think we need a short summer dewshield or even none at all, since it can be 22C here on warm nights.

I'll ask my optical engineering guru about the optimal cable route but it looks as if it's an non-issue as long as you use a curve.

Olly

[gorann]

21 hours ago, ollypenrice said:

Maybe it's not just the heat: the stirring of the air by the fan probably helps as well? But it's great to hear that dewing isn't a problem.

Your cable loops from the camera are some distance from the corrector. I was going to run ours down the camera side and then in front of the corrector so as to be as far out of focus as possible but perhaps this isn't necessary.

Olly

The ASI2600 has virtually the same diameter (90 mm) as the cetral obstruction (93 mm) so running cables along the side of the camera may in itself cause diffraction if they stick out a bit. I have not noticed any diffraction artefacts in the way I have the cables at the back of the camera, so it seems to work fine. Some pessimists have commented on the possibility that the heat from the camera and the fan could cause some turbulence but I have not seen that anyone has shown that this is a real problem that affects the images. In any case I cannot see how it could be avoided since I am quite sure that the corrector plate is too much of a dew magnet to allow the scope to be used without a dew shield.

[ollypenrice]

On 07/07/2021 at 12:14, gorann said:

The ASI2600 has virtually the same diameter (90 mm) as the cetral obstruction (93 mm) so running cables along the side of the camera may in itself cause diffraction if they stick out a bit. I have not noticed any diffraction artefacts in the way I have the cables at the back of the camera, so it seems to work fine. Some pessimists have commented on the possibility that the heat from the camera and the fan could cause some turbulence but I have not seen that anyone has shown that this is a real problem that affects the images. In any case I cannot see how it could be avoided since I am quite sure that the corrector plate is too much of a dew magnet to allow the scope to be used without a dew shield.

Was it Heisenberg who said, on his deathbed, that he had two questions for god, quantum mechanics and turbulence? He said he thought he might get an answer on quantum mechanics. If your pessimists are beyond both Heisenberg and god then I will happily ignore them!

Your argument makes perfect sense and I will do as you did.

Some bits of progress:

Pier attacked with drill and angle grinder (surrounded by wet sheet to avoid spraying nearby rigs with iron filings) to allow optimal and collision-free placing of mount. We can image down to 30 degrees now. The pier originally had a square top.

Electric focus arrived today and was duly installed:

Camera also arrived.  Am now going slightly mad trying to sort out the backfocus options and the merits of the Pierro Astro squidge-free adapter plate, an item which need not keep anyone but RASA owners awake!

 

Olly

 

Edited July 8, 2021 by ollypenrice

[tomato]

Definitely not a fan of the Celestron squidgy material, given how precise the tilt adjustment needs to be. I'm not sure what their thinking was to include this, it isn't as if you are tightening the retaining ring onto glass.

[ollypenrice]

27 minutes ago, tomato said:

Definitely not a fan of the Celestron squidgy material, given how precise the tilt adjustment needs to be. I'm not sure what their thinking was to include this, it isn't as if you are tightening the retaining ring onto glass.

On the other hand the compression in this context is minor. You don't tighten the squidgy plate down with bolts perpendicular to it, which would apply real pressure, but only with that kind of jam jar lid affair which fits over it to hold it down. I'll talk to Paul tomorrow about the Pierro Astro Squidgeless Plate at a walloping 109 euros . Maybe that really is the way to go...  All thoughts welcome.

Olly

Edited July 8, 2021 by ollypenrice

[gorann]

Not sure what the "Pierro Astro squidge-free adapter plate" is. Does it say "Artesky" on it or has Pierro made his own adapter?

[ollypenrice]

8 hours ago, gorann said:

Not sure what the "Pierro Astro squidge-free adapter plate" is. Does it say "Artesky" on it or has Pierro made his own adapter?

Yes, it's the Artsky adapter. I've ordered one.

Olly

[gorann]

1 hour ago, ollypenrice said:

Yes, it's the Artsky adapter. I've ordered one.

Olly

Great! I made two modifications of my Artesky adapter. The most important one was to drill two small shallow holes in it so I can use a tool to unskrew it from the camera since I realized that it could easily get stuck and there is no way to grip it when it is inside the Celestron retention ring. The second modification was to put teflon tape (PTFE tape) on the surface facing the scope. That creates a perfect degree of friction so I can rotate the camera using minor force to help with framing. The tape is only 0.1 mm thick so it will have a minor impact on the sensor distance.

About sensor distance: The Artesky adapter comes with a metal distance ring. I use that when I have a filter in the adapter and do not use it when there is no filter.

Göran

[ollypenrice]

3 hours ago, gorann said:

Great! I made two modifications of my Artesky adapter. The most important one was to drill two small shallow holes in it so I can use a tool to unskrew it from the camera since I realized that it could easily get stuck and there is no way to grip it when it is inside the Celestron retention ring. The second modification was to put teflon tape (PTFE tape) on the surface facing the scope. That creates a perfect degree of friction so I can rotate the camera using minor force to help with framing. The tape is only 0.1 mm thick so it will have a minor impact on the sensor distance.

About sensor distance: The Artesky adapter comes with a metal distance ring. I use that when I have a filter in the adapter and do not use it when there is no filter.

Göran

Yet again, thanks for this excellent information. I've done similar drillings myself but don't have a nice adjustable device like yours. I hope that a quick internet search and order will put that right!

Olly

[gorann]

7 hours ago, ollypenrice said:

Yet again, thanks for this excellent information. I've done similar drillings myself but don't have a nice adjustable device like yours. I hope that a quick internet search and order will put that right!

Olly

Yes I found it on Amazon or ebay, cannot remeber which one but I remember it was cheap so I bought two which doubles the chance of finding the tool when I need  it.

Edited July 9, 2021 by gorann

[ollypenrice]

4 hours ago, gorann said:

Yes I found it on Amazon or ebay, cannot remeber which one but I remember it was cheap so I bought two which doubles the chance of finding the tool when I need  it.

This policy doesn't always work for me. I specialize in losing 10mm spanners. Buying ten at a time has not solved the problem...

lly

[Ibbo!]

8 minutes ago, ollypenrice said:

This policy doesn't always work for me. I specialize in losing 10mm spanners. Buying ten at a time has not solved the problem...

lly

For me it is Allen keys - does not matter what the size as its that one missing from the set.

[Xiga]

This is going to be fascinating to watch@ollypenrice! Can't wait to see your results with this once you've ironed out all the kinks.

ps - TAIC recently did a presentation on the RASA, specifically the 8" version. Could be worth a skim in case it contains a few nuggets of information. 

 

[tomato]

Thanks for this @Xiga. Interesting that he encountered issues with the focus which required regular refocus, that’s contrary to myself and Gorann’s experience with the RASA.

The flat USB cables supplied with ZWO cameras don’t have a great reputation for reliability, so might be good to change this for a round profile cable.

I have never switched off the circulation fan on the scope when imaging, so I’ll do this next time.