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Celestron 8" RASA images yet?

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#1 andysea

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Posted 19 December 2018 - 11:01 PM

I'm looking for images - maybe even single subs - taken with the 8" rasa. I am trying to understand the quality of the stars that this telescope can produce. So far I have seen a few  images that were pretty bad when seen at 100%. I know it's a new scope but has anyone used it with satisfactory field flatness and good stars to the corners of a micro 4/3 sensor? I am also curious about the FWHM numbers that people are getting with it.

Anyone?


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#2 bobzeq25

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Posted 19 December 2018 - 11:20 PM

Where have you seen any images?  Availability is limited, I've seen a few websites saying February.



#3 jeffweiss9

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Posted 19 December 2018 - 11:25 PM

I have the same question about the 8" RASA as I've been thinking about it with a Canon M6 on it (or maybe a QHY183C).

Cheers,
Jeff



#4 bobzeq25

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Posted 20 December 2018 - 12:01 AM

I have the same question about the 8" RASA as I've been thinking about it with a Canon M6 on it (or maybe a QHY183C).

Cheers,
Jeff

The 183C (which is what I plan to use) fits easily within the central obstruction.  The M6 goes over by almost an inch in width. 



#5 andysea

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Posted 20 December 2018 - 01:33 AM

Yeah I think the color cmos cameras are the best fit for this scope. I’d like to order one but I’d also like to see some high quality data from it first.

Edited by andysea, 20 December 2018 - 01:34 AM.


#6 akulapanam

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Posted 20 December 2018 - 04:32 PM

Baader has some posted.  https://www.baader-p...en-with-rasa-8/ .  Really only a good platform for OSC CMOS / CCD.



#7 bobzeq25

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Posted 20 December 2018 - 04:56 PM

Baader has some posted.  https://www.baader-p...en-with-rasa-8/ .  Really only a good platform for OSC CMOS / CCD.

How so?  The page has HaRGB, others.  I plan on using a 183C for OSC (RGB data), supplemented by a 183M for L or Ha.  A camera swap is trivial.


Edited by bobzeq25, 20 December 2018 - 05:11 PM.


#8 Kaydubbed

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Posted 20 December 2018 - 05:01 PM

Yeah I think the color cmos cameras are the best fit for this scope. I’d like to order one but I’d also like to see some high quality data from it first.

 

 

There is not enough backfocus for a filterwheel, but a asi1600mm would pull hard-to-get NB data very fast. You would just only be able to do one filter at a time.

 

The consensus for OSC is that the asi294mc is the best choice due to its deep wells in combination with F/2 would make getting hundreds of lights a snap with short exposures. Of course F2 means any OSC will have shorter exposure times but the asi294 would just benefit the most. 



#9 Kaydubbed

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Posted 20 December 2018 - 05:04 PM

There must have been some major QA issues to go from December 2018 to Spring 2019. I'm glad I cancelled my pre-order. I feel bad for the folks who have been on the pre-order list for 6 months now and will be on it probably for another 4 or more, but that's a risk you take for a hot new product. 



#10 andysea

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Posted 20 December 2018 - 06:40 PM

The stars in those images have artifacts caused by the camera cabling. I was thinking that perhaps the best way to address that would be to fabricate spider vanes and then run the cables along them.


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#11 akulapanam

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Posted 20 December 2018 - 08:29 PM

How so? The page has HaRGB, others. I plan on using a 183C for OSC (RGB data), supplemented by a 183M for L or Ha. A camera swap is trivial.


Camera swap is unfortunately not trivial with cheap cameras and fast optics. Like all fast systems tilt is a major issue so if you get it right you don’t want to swap out. That is why a filter slider is the ideal option BUT the 8” as so little backfocus it might not be possible. A more expensive ccd camera might (say an Atik 4xx) might not present the same challenge.

#12 akulapanam

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Posted 20 December 2018 - 08:29 PM

The stars in those images have artifacts caused by the camera cabling. I was thinking that perhaps the best way to address that would be to fabricate spider vanes and then run the cables along them.


Ideally an arc pattern will completely eliminate the problem. I never managed to accomplish that with Hyperstar but several have.

#13 Churmey

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Posted 20 December 2018 - 10:44 PM

Just wanted to point out the concern about the field of the RASA scopes. I have the 11" version and the field is very flat (I've had up to a APS-C on it but it's rated for FF coverage). However, it wasn't this way straight out of the box - my collimation was off.  If you receive a RASA and you notice that your collimation is off, do not try and collimate it yourself. It VOIDS Celestron's first 30 day collimation warranty. I simply took a video of my in/out star focus, and sent it to Celestrion. They immediately sent me a RGA label and it was shipped back to them for collimation. When i received it back, it was perfect and it has remained so.

 

I thought i would point this 30 day collimation warranty out because there was NO mentioning of it when i purchased it, and the manual had no mentioning of it. I almost got my tool kit out to give it a go but instead I luckly reached out to Celestion via website chat - that's were i found it all out.  Looking forward to seeing everyone's first light with the 8" - it should be a best seller :)


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#14 freestar8n

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Posted 20 December 2018 - 11:33 PM

Just wanted to point out the concern about the field of the RASA scopes. I have the 11" version and the field is very flat (I've had up to a APS-C on it but it's rated for FF coverage). However, it wasn't this way straight out of the box - my collimation was off.  If you receive a RASA and you notice that your collimation is off, do not try and collimate it yourself. It VOIDS Celestron's first 30 day collimation warranty. I simply took a video of my in/out star focus, and sent it to Celestrion. They immediately sent me a RGA label and it was shipped back to them for collimation. When i received it back, it was perfect and it has remained so.

 

I thought i would point this 30 day collimation warranty out because there was NO mentioning of it when i purchased it, and the manual had no mentioning of it. I almost got my tool kit out to give it a go but instead I luckly reached out to Celestion via website chat - that's were i found it all out.  Looking forward to seeing everyone's first light with the 8" - it should be a best seller smile.gif

If I understand this warranty - it means that you can ship it back for adjustment within 30 days of receiving it if you want the collimation tweaked.  But if you go ahead and tweak it yourself you haven't voided anything other than the ability to have them adjust it - within 30 days.  I would just do it myself rather than ship it to them.

 

The RASA manual says you may need to tweak collimation after transport - and I sure would expect to.  But I guess if you see a severe problem that looks hard to fix with collimation then you might want to ship it back right away.

 

And I guess the 30 day warranty applies to all their scopes.  I didn't even know about it.  I would tweak collimation on any scope I received through the mail - if it has collimation adjustments for the purpose.

 

For something with such a flat and well corrected field - it might even need tweaks for different cameras - due to slightly different sensor tilt.

 

Frank


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#15 Churmey

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Posted 20 December 2018 - 11:42 PM

If I understand this warranty - it means that you can ship it back for adjustment within 30 days of receiving it if you want the collimation tweaked.  But if you go ahead and tweak it yourself you haven't voided anything other than the ability to have them adjust it - within 30 days.  I would just do it myself rather than ship it to them.

 

The RASA manual says you may need to tweak collimation after transport - and I sure would expect to.  But I guess if you see a severe problem that looks hard to fix with collimation then you might want to ship it back right away.

 

And I guess the 30 day warranty applies to all their scopes.  I didn't even know about it.  I would tweak collimation on any scope I received through the mail - if it has collimation adjustments for the purpose.

 

For something with such a flat and well corrected field - it might even need tweaks for different cameras - due to slightly different sensor tilt.

 

Frank

That's how I understood it Frank.  I personally believe the collimation was off due to initial factory assembly. The way it's designed, it's very rigid after things are set, so I suspect that it will hold for a very long time; only time will tell.  Also, to collimate the RASA it seems more tedious than, say, a SCT or Newt or Hyperstar.... so i'm sure glad I didn't have to mess with it.



#16 andysea

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Posted 20 December 2018 - 11:44 PM

I’m afraid that such a fast instrument would need collimation pretty much every time it gets transported, no?



#17 Churmey

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Posted 20 December 2018 - 11:56 PM

I’m afraid that such a fast instrument would need collimation pretty much every time it gets transported, no?

It  makes me laugh thinking about my story as it relates to this..... As i said, it looks rigid too me and i suspect it to hold a long time. I've not transported mine yet so i can't verify. However, here is what i can say. After Celestron completed the readjustment  (on the west cost), they shipped it all the way across country to where I live in the southeast .  I have an Arlo camera mounted on my front porch and it captures the mail carriers (almost daily) delivering to my front porch.  A UPS lady delivered my package that day and you could see her dragging the big box through my yard, and bumping it accross my two steps. I cringed!  I mounted it and my field was fixed / flat.  I was pretty impressed as i just knew i was going to have to send it back again!


Edited by Churmey, 21 December 2018 - 12:05 AM.

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#18 Kaydubbed

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Posted 21 December 2018 - 09:47 AM

I’m afraid that such a fast instrument would need collimation pretty much every time it gets transported, no?

 

 

Maybe even multiple times during long imaging sessions



#19 bobzeq25

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Posted 21 December 2018 - 10:45 AM

The permanent RASA configuration will surely require less collimation than the addon Hyperstar.  And many people image happily with Hyperstar.

 

Yes, it's an issue, particularly when the scope has been shipped by common carrier.  But not likely as much of one as it is with a Ritchey-Chretien (my 6RC arrived in extremely bad collimation, the spikes were doubled up), and some people image with those too.


Edited by bobzeq25, 21 December 2018 - 10:47 AM.

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#20 andysea

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Posted 21 December 2018 - 12:49 PM

That's good to know. I am not afraid of collimating a scope. I regularly do that with my RCOS and it's very straightforward.

Clearly there isn't anything as fast as the 8" RASA in the same focal range. Even the Epsilon 180 is a whole stop slower.

Before placing an order I'd still like to see high quality data produced with this scope.

It will probably come in the near future as people start taking delivery of their samples. 
I have seen stunning results from the RASA 11 including a recent APOD and that is encouraging.


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#21 lucutes

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Posted 21 December 2018 - 03:48 PM

I have to respectively disagree that the IMX294 would be a good sensor. Celestron quotes that sensors with pixels less than 5 microns work best but the 294 is 4.63 microns. Ideally the best sensor would be one with small pixels such as the IMX183, or 193. The QHY247C would be a good compromise between chip size and pixel size. Another good contender would be the ASI1600MC neither of which I have. I'll try out the 071 and go from there.

 

I purchased the RASA8 LPS mostly for the UV/IR cut as there currently is no way of threading in a standard filter into the imaging train. I left a comment at the bottom of Baader's article and they replied as below.

 

 

RASA 8”
December 15, 2018 at 6:56 am
Wow, nice work. How did you use the filters on the ASI1600?
Reply ↓
Team Baader Planetarium
December 17, 2018 at 10:10 am
This was a unique solution to mount the filters, we are working on filter changers and adapters

Looks promising. 

Due to clouds for the foreseeable future I doubt I will have any images until late January. I hope to see how much light falloff is at the edges with the ASi071 and then decide whether to go for a QHY247 or 1600 colour sensor. I'll try and post some equipment shots this week on my Flickr page. 


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#22 Churmey

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Posted 21 December 2018 - 04:14 PM

I purchased the RASA8 LPS mostly for the UV/IR cut as there currently is no way of threading in a standard filter into the imaging train

I use the Starizona Filter slider, to accommodate my filters, in my R-11.  Works great.


Edited by Churmey, 21 December 2018 - 04:15 PM.

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#23 akulapanam

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Posted 22 December 2018 - 01:18 AM

I use the Starizona Filter slider, to accommodate my filters, in my R-11.  Works great.

The backfocus on the RASA 8" is substantially less than the RASA 11"


Edited by akulapanam, 22 December 2018 - 01:19 AM.

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#24 Tattooeddeputy

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Posted 09 February 2019 - 08:45 PM

You can use this starzonia filter drawer system on the Rasa 8". Only if using asi1600mm and asi 183mm. It's the only 2 starzonia as worked it out for. Per Scott at starzonia. I have one. Fits fine. Works well.
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#25 bobzeq25

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Posted 09 February 2019 - 10:26 PM

Bac

 

You can use this starzonia filter drawer system on the Rasa 8". Only if using asi1600mm and asi 183mm. It's the only 2 starzonia as worked it out for. Per Scott at starzonia. I have one. Fits fine. Works well.

Backfocus on those cameras is 17.5mm, so presumably any camera with that or less should work.  Or does the Starizona system allow removal of the T2 ring, which could make it 6.5mm? 




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