Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Rasa 8 opinions

  • Please log in to reply
41 replies to this topic

#1 jprideaux

jprideaux

    Explorer 1

  • -----
  • topic starter
  • Posts: 68
  • Joined: 06 May 2018
  • Loc: Richmond, VA

Posted 08 February 2019 - 06:43 PM

It looks like some preliminary Rasa 8s may have been shipped fulfilling some pre-orders but there is not a lot of information yet out there on how well it works and how well it pares with certain cameras.

 

I'm interested in the Rasa 8 mainly for EAA (or Observational AP, near real-time viewing).  

 

For EAA simplicity, I'm considering a Rasa 8 on an iOptron Az Pro paired with either a ASI183 or ASI294 camera.  The alt-az mount would only allow perhaps 10 second exposures, but that is all that would be needed for EAA as I understand it with this fast system with 8" of aperture.  I know people say that the ASI294 would under-sample but may be fine for the lower expectations of EAA (especially with skies with poor seeing).   

 

Is there anyone out there that has gotten their hands on a Rasa 8 yet or who has expert knowledge to provide some valued opinions on using the Rasa 8 for EAA?  And opinions about using the Rasa 8 for EAA on an alt-az mount or the various camera choices?

 

The other system I have my eye on is the Vaonis Stellina which should start being shipped soon as well.  Perhaps we are still a couple months away, though,  from getting good field reports for either of these systems...

 

Thanks,


Edited by jprideaux, 08 February 2019 - 09:50 PM.


#2 OleCuss

OleCuss

    Vanguard

  • *****
  • Posts: 2230
  • Joined: 22 Nov 2010

Posted 09 February 2019 - 05:41 AM

It looks like no one else has seen reports from actual 8" RASA users.

 

But folk seem to have been very happy with the 11" version for whatever that is worth.



#3 DonBoy

DonBoy

    Apollo

  • *****
  • Posts: 1237
  • Joined: 06 Sep 2007

Posted 09 February 2019 - 05:34 PM

https://www.cloudyni...t/#entry9105097

 

You may need longer than 10sec with the ASI183MC.


  • OleCuss likes this

#4 jprideaux

jprideaux

    Explorer 1

  • -----
  • topic starter
  • Posts: 68
  • Joined: 06 May 2018
  • Loc: Richmond, VA

Posted 09 February 2019 - 06:49 PM

 

 

Posted Today, 05:34 PM

https://www.cloudyni...t/#entry9105097

 

You may need longer than 10sec with the ASI183MC.

Yeah, that is the only other thread I've seen on the Rasa 8 for people who have actually received one.

 

In that thread, they are more in AP mode versus EAA mode, though.

 

I guess in time more will come out.  



#5 at4768

at4768

    Lift Off

  • *****
  • Posts: 3
  • Joined: 10 Jan 2019

Posted 09 February 2019 - 07:17 PM

Mine is sitting in the basement, haven't used it yet


  • lucutes likes this

#6 lollywater

lollywater

    Sputnik

  • -----
  • Posts: 39
  • Joined: 10 Feb 2013
  • Loc: Bendigo Victoria Australia

Posted 10 February 2019 - 12:52 AM

Nah,I am definitely not in AP mode. The reason for buying the RASA8 was to get 10 sec exposures. With ASI 294 I think it can  do that. Unfortunately with a combination of holidays and then a broken wrist, I havent been able to get the scope out. As can be seen in the only images I have,there is obvious mirror tilt so I am sending it back to the US for collimation and adjusting 

 I think it will be a great scope for EAA, not so sure for the Astrophotographers who want the perfect image.

This is the only image I have with a 10 sec exposure. It was taken Dec 22 and the moon was bright. ngc 253   10" x6 stack on sharpcap  ZWO 294 uncooled

 

I have been waiting for posts to appear . I presume the mirror tilt is not a common problem. 

 

10-x-6-253.jpg

 

also

horsehead 15" x4 stack on sharpcap ZWO 294 on the RASA8 same night in Dec

 

15sx4 300k.jpg

 

 

cheers

Paul


Edited by lollywater, 10 February 2019 - 02:32 AM.

  • mclewis1, roelb and Kegan128 like this

#7 jprideaux

jprideaux

    Explorer 1

  • -----
  • topic starter
  • Posts: 68
  • Joined: 06 May 2018
  • Loc: Richmond, VA

Posted 10 February 2019 - 02:09 PM

Thanks.  I look forward to more posts in the coming weeks as people have actual opportunities to use the RASA 8 with clear skies.

 

I have seen the two (so far) "Unboxing/First impressions" You tube videos but those were not about actually using it.

 

Dylan O'Donnell  (StarStuff)

https://www.youtube....h?v=TpHlEz88eJc

 

 

Roswell Astronomy

https://www.youtube....h?v=ST3vRoU7JHo


Edited by jprideaux, 10 February 2019 - 02:11 PM.

  • roelb likes this

#8 FWHM

FWHM

    Lift Off

  • -----
  • Posts: 17
  • Joined: 10 Feb 2019

Posted 10 February 2019 - 06:08 PM

I purchased the RASA 8 in December 2018 and my experience with the astrograph has been excellent.

I highly recommend the RASA 8. I also have a SCT 9.25 and not sure if I will use it again due to the amazing RASA 8.


The main reason for purchasing the RASA 8, was to increase the sky coverage from 21.9 x 16.4 arc-minutes (SCT 9.25 f/6.3 with Atik Infinity) to a sky coverage of 107.3 x 85.8 arc-minutes (RASA- Atik 460ex).

The other reason was to have a faster exposure. For example, a 1 hour RASA F/2 exposure is equivalent to 9 hours at F/6.3. Life is short and time is precious.

I see more of the universe and faster and that is a great incentive to get the RASA.

The RASA 8' is light and portable. I have some of the best dark skies, one hour from my house. The RASA 8 was the right size for this task and for me.


My cameras are CCD's and I can't comment on Cmos-camera & RASA at this time.I am currently using two cameras, The Atik Infinity and the Atik 460ex.

Most people say that the pixel area should be between 1 and 2 for good imaging, however, I get very good results with the RASA 8 at 3.3 (under sampling).


The RASA 8 with the Atik infinity with a pixel size of 6.45 x 6.45 produces  a pixel area of 3.3 pix and great photos.

The square shape of the Atik infinity camera is larger than the 'lens group cell' and creates very large diffraction spikes. Kind of cool actually!

The RASA 8 with the Atik 460ex with a pixel size of 4.54 x 4.54 produces a pixel area of 2.3 pix and amazing photos.

The round shape of the Atik 460ex is perfect for the RASA 8 and the diffraction spikes are small.

I will share some images with you later on, but before I do this, I would like to share a few observations and details.

First item, Dylan O has a great review of this astrograph, you may want to review his information. I want everyone to know, the light pollution Filter is not included with the RASA 8 as stated in the review.


Also, the feather touch focuser is not a component of the RASA 8. For myself, I got confused between the RASA 11 and RASA 8 spec. sheets.

As for the focusing system of the RASA 8, I have not had any problems even when imaging at -20 C here in Canada.


Using a Bahtinov mask, I would start an imaging session at FWHM= 3.0 to 4.5 and have the same FWHM value 6 hours later.  This information indicates to me, nothing move, nothing shifted on all of my observations sessions with the RASA 8.(9 sessions 6+ hours per session so far...)

I had one minor issue with removing the optical window.  Make sure you use an appropriate tool to remove the window. It is impossible to remove the optical window, just with your finger or a sharp object.


This optical window removal tool should have been provided with the astrograph, but it is what it is.

I give the Celestron RASA 8, a very high 5/5 rating, including the service I received from Celestron and All-Star Telescope (https://www.all-startelescope.com) where I purchased the RASA 8.


Images produced with RASA 8 are in my opinion,amazing if I compared them to my SCT 9.25 F6.3, using the same camera.

 

Links to 'RASA 8' images taken in a city with Bortle index=8:

RASA 8 Images :

 

A summary for January


The Monkey Head Nebula in Orion:  


M42:

 

IC 5146 with Atik Infinity:

 

Hope this information is useful.

I am not a promoter of any of the co or products listed above. This review is my own experience with RASA 8 for the pure enjoyment of discovering the universe.

Clear skies,

R.


Edited by FWHM, 10 February 2019 - 06:18 PM.

  • OleCuss, roelb, Kegan128 and 1 other like this

#9 OleCuss

OleCuss

    Vanguard

  • *****
  • Posts: 2230
  • Joined: 22 Nov 2010

Posted 10 February 2019 - 07:41 PM

Much appreciated!  Unfortunately I can't really get one at this time and that means that your wisdom just generates envy for me.

 

What makes me even more interested is that I do have the ASI183MM which has about the same diagonal measurement and smaller pixels.  What you've got makes me even more agitated about getting that RASA 8.



#10 jprideaux

jprideaux

    Explorer 1

  • -----
  • topic starter
  • Posts: 68
  • Joined: 06 May 2018
  • Loc: Richmond, VA

Posted 10 February 2019 - 07:44 PM

FWHM,  
 
Thanks for your detailed description of your experiences over the last month with the RASA 8.  I'm sure many on cloudy Nights will find this information valuable.
 
Can you comment a bit on exposure times, stacks, any filters used, and how much post-processing effort you did? 
 
Again, beautiful pictures.  Were all the images in the following compilation image from your dropbox all taken with the Rasa 8?

#11 descott12

descott12

    Viking 1

  • -----
  • Posts: 705
  • Joined: 28 Sep 2018
  • Loc: Charlotte, NC

Posted 10 February 2019 - 08:26 PM

 

 

Can you comment a bit on exposure times, stacks, any filters used, and how much post-processing effort you did? 

 

 

 

Yes, I am also curious about your total integration time.  The M31 photo is amazing so I am thinking this was not purely EAA and there was alot of post-processing involved.

 

Also, general question: How goes the RASA compare to  Evo 8 + Hyperstar? My understanding is that they should be pretty similar optically.



#12 Don Rudny

Don Rudny

    Surveyor 1

  • *****
  • Posts: 1621
  • Joined: 21 Mar 2013
  • Loc: Mauna Kea, Hawaii

Posted 11 February 2019 - 12:02 AM

Yes, I am also curious about your total integration time.  The M31 photo is amazing so I am thinking this was not purely EAA and there was alot of post-processing involved.

 

Also, general question: How goes the RASA compare to  Evo 8 + Hyperstar? My understanding is that they should be pretty similar optically.

 

To respond to Dave’s general question, I have used both a RASA and Hyperstar setups, but at 11” not 8”.  I found both excellent and great for EAA.  My preference is the C11 with Hyperstar for a couple of reasons.  First, with the RASA, you are locked into one focal length.  One may argue that you can zoom or use a ROI with your camera, but the resolution will not be as good as changing the focal length of the scope.  The C11 or 8  with HS can also be used at f/6 and f/10 for planetary nebula and smaller galaxies.  The second advantage to a standard or Edge C11 or 8 with Hyperstar is that you can use it visually as well.  I didn’t see a drastic difference in image quality with each.  I searched my image library and found these two images as an example.  Same camera same location.  Not sure conditions are identical, but they are close.  The HS image has some reflection caused by Alnitak.  Not sure that is a factor with the HS, but I only see that condition with very bright stars in the image.

 

The camera is an SX Ultrastar C.  The sensor diagonal is 11mm.  One reason to get a RASA is for those who use a full 35mm sensor, the corrected field will be large enough to fit it.  The HS has a smaller corrected field of about 26mm fitting many larger sensors, but not full size.  The C11 with HS has a slightly wider FOV at f/2 v. f/2.2 for the RASA.

 

RASA 11” Capture

 

10257FAA-CDB9-4673-B7D8-4711FAE3C6D7.jpeg

 

C11 Edge Capture

 

54E278AE-6266-43D1-9CD0-4BA43D668A2B.jpeg


  • rob961, roelb and FWHM like this

#13 FWHM

FWHM

    Lift Off

  • -----
  • Posts: 17
  • Joined: 10 Feb 2019

Posted 11 February 2019 - 04:23 AM

all of my January photos were taken with the Rasa 8 and acquired and processed by me.

i usually take 30 to 60 secs exposure and stack with DSS after i finish my video viewing with the atik infinity software.

i am not sure what you mean by What is integration time?

if you are asking what was the time it took to process the image?

 

the time to process is usually about one hour. 

Because i am new to this, the processing is very simple.

Crop the image of noise. wipe the image of light pollution, stretch the histogram for colour

i usually don't alter colors, it depends if i feel i have Noise, usually glow with my setup.

with my sct, the noise was vignetting, but now the noise is glow. (I think i am getting frost between the optical window and the camera). I use the Rasa fan all night. Expensive of batteries. I wish Celestron would have the option to purchase a12 v adapter for the fan.

 

all photos are taken without a filter.

All of the January photos are taken in the city at bortle index of 8.

(i am always amazed at what i get despite the terrible light pollution).

 

my choice of ccd with the atik infinity was the correct one. For me , video astronomy makes sense.

 

The purchase of The Rasa was the right choice for me after reading and discovering all options.

 

i keep my setup simple.

When i first saw the difference between F6.3 and F2 and the quality of the image with the Rasa 8 and the details, i was amazed.

 

 

My first impression with the Rasa 8 for me was the different colors of the stars and a sense of 3D  in the image, something i did not get with my sct 9.25 with reducer.

 

 


Edited by FWHM, 12 February 2019 - 03:31 AM.


#14 lollywater

lollywater

    Sputnik

  • -----
  • Posts: 39
  • Joined: 10 Feb 2013
  • Loc: Bendigo Victoria Australia

Posted 11 February 2019 - 05:04 AM

Thanks for your posts FWHM. That is very reassuring for me. Once the mirror is readjusted I am confident that it will be a great scope for my EAA

cheers

Paul



#15 jprideaux

jprideaux

    Explorer 1

  • -----
  • topic starter
  • Posts: 68
  • Joined: 06 May 2018
  • Loc: Richmond, VA

Posted 11 February 2019 - 08:57 AM

In the Roswell Astronomy YouTube link I posted earlier, he mentioned that you might need a "spanner wrench" to get the optical window out in order to install the light-pollution filter.  I didn't know what a spanner wrench was so I searched a bit and saw this:

https://www.youtube....h?v=g4l67YlZXXQ that describes inexpensive ones used for lens repair.

 

I'm also struggling to decide whether to go Rasa or (CST + hyperstar). And if CST, whether to upgrade to Edge.   I realize the RASA has a lot of appeal because it is "shinny and new" but I want to make the best decision for how it can benefit me in what I want to do (and what I haven't yet thought of that I will later want to do).  Ha. 

 

As I understand it, the RASA has some advantages (to Celestron) in manufacturability with savings that can be reflected in the cost (to the consumer).  With the positioning of the corrector lenses inside the tube, the correcting lenses can be less complicated than what is needed at the hyperstar location. The RASA also gets a bit larger image circle relative to the hyperstar.  Although, to reduce under-sampling and to frame the most number of popular celestial objects, some people are looking at the ASI183 with the RASA which would only use a small portion of the image circle and any larger FOV advantage of the RASA over the CST + hyperstar would be lost.  The RASA would only work to its FOV potential with a camera with a sensor large enough to take advantage of its larger image circle.  Of course, if your objects of interest are smaller than that, that larger image circle won't matter.  The RASA does have the advantage that you don't have to take on and off the correcting lens every time you use it and less collimation issues because you are not fiddling with critical lens groups.  Of course with RASA, you only have F2.   With the CST, you can also have F7 (with different reducer), F10,  F20 (with barlow), and visual.  Where I live, light pollution is so bad that visual is almost a thing of the past (thus my interest in EAA).  I would like to see planets from time to time with a larger scope than my Questar.  I could either do CST + hyperstar (and take hyperstar off and add barlow) or get RASA and also another larger dedicated planet scope (perhaps a 7" Maksutov-Casigrainian).  For portability, 7 or 8 inches in aperture is about as big as I want to go.

 

I'm also struggling in deciding on a mount.  I like the idea of an Alt-Az mount for simplicity of use but I also don't want to spend $1300 on an iOptron Az pro (with tripod) only to then decide I want to try AP and want an equatorial mount for longer exposures.  On the other hand, if I initially get the equatorial mount and discover that I mainly just like EAA and can get away with short-enough exposures not needing more precise tracking, I would hate to have to polar align every time I just want to get a quick (EAA style) look at something.   I assume everyone goes through similar decision processes (with perhaps different details).  


Edited by jprideaux, 11 February 2019 - 09:05 AM.


#16 OleCuss

OleCuss

    Vanguard

  • *****
  • Posts: 2230
  • Joined: 22 Nov 2010

Posted 11 February 2019 - 09:43 AM

If the sole intent is OAP, I'd probably go with the Corrected SCT (CSCT) like the EdgeHD or the similar Meade product.  You'll have more flexibility of use and you may some day go to a dark site.

 

I'm betting most who use the 8" RASA for OAP are going to be under-sampling pretty badly and probably not even notice that.  So the optical and mechanical excellence of the RASA won't be very evident and you'll not have the ability to use the instrument at the various focal lengths you could use with the Hyperstarred CSCT.

 

So far as I know, you don't have to remove the Hyperstar unless you plan to do something which will risk hitting it.

 

It's perfectly fine to go with an A-Z mount if you can get one which is sufficiently robust.  A good CGEM may give you more imaging options.  Either way you can be happy.

 

BTW, there are a few fiddly things I'd be thinking about before I got either system.

 

Do you plan to use a Bahtinov mask and, if so, do you know where to get or how to make one to fit either the RASA with the camera in place or the CSCT with the Hyperstar and camera in place?  There may be readily available fixes for this but I don't know it.

 

Have you figured out how you are going to do your flats with the camera or camera with Hyperstar in place?  Again, it may be simplicity itself, but I am not sure of the preferred methods.



#17 jprideaux

jprideaux

    Explorer 1

  • -----
  • topic starter
  • Posts: 68
  • Joined: 06 May 2018
  • Loc: Richmond, VA

Posted 11 February 2019 - 09:59 AM

For either (CSCT + hyperstar) or RASA, I'm hopeful that the use of a due shield with a hole to route the cables from the camera would allow for placement of the  Bahtinov mask or a cover to totally block the light for flats.  It is unknown (to me) whether the due shield sold by Celestron would work for this or whether some alternative due shield would need to be sourced or crafted.



#18 descott12

descott12

    Viking 1

  • -----
  • Posts: 705
  • Joined: 28 Sep 2018
  • Loc: Charlotte, NC

Posted 11 February 2019 - 11:23 AM

I use the Celeston dew shield and mybahtinov mask fits very nicely over the end. I drilled two  holes in the shield to pass the USB and power cables and it works perfectly. The drill holes also help organize the cables so they aren't just dangling


  • OleCuss likes this

#19 FWHM

FWHM

    Lift Off

  • -----
  • Posts: 17
  • Joined: 10 Feb 2019

Posted 12 February 2019 - 03:57 AM

Nah,I am definitely not in AP mode. The reason for buying the RASA8 was to get 10 sec exposures. With ASI 294 I think it can  do that. Unfortunately with a combination of holidays and then a broken wrist, I havent been able to get the scope out. As can be seen in the only images I have,there is obvious mirror tilt so I am sending it back to the US for collimation and adjusting 

 I think it will be a great scope for EAA, not so sure for the Astrophotographers who want the perfect image.

This is the only image I have with a 10 sec exposure. It was taken Dec 22 and the moon was bright. ngc 253   10" x6 stack on sharpcap  ZWO 294 uncooled

 

I have been waiting for posts to appear . I presume the mirror tilt is not a common problem. 

 

 

 

also

horsehead 15" x4 stack on sharpcap ZWO 294 on the RASA8 same night in Dec

 

 

 

 

cheers

Paul

Hi Paul,

in your photo, i don't see anything wrong with your optical train. Your photos are underexposed and have a low signal to noise ratio. Next time, start with a minimum time exposure of 35s. Also i usually stack a minimum of 30 lights. I see you stacked 4 with your horsehead flame nebula. Next time stack a minimum of 20 light frame or more. Do you mind if i use your horsehead jpg and process it for 10 min. I believe you have hidden data in your Stack and i may be able to improve the s/ n ratio.

 

let me know. I know this thread is about eaa, but i would like to demonstrate that eaa can lead to taking some amazing photos. If you agree, i will process your jpg and post the result tomorrow.

clear skies,

r



#20 lollywater

lollywater

    Sputnik

  • -----
  • Posts: 39
  • Joined: 10 Feb 2013
  • Loc: Bendigo Victoria Australia

Posted 12 February 2019 - 04:23 AM

Hello FWHM,

Yeah that would be fine.I have a habit of posting bad images on another forum,but occasionally I get right

I only posted those 2 images in answer to a question about 10 second exposures. My aim with EAA is to get total exposure down to 1 minute at most and I think the RASA 8 is quite capable of that

I did a 45"x 4 of the horsehead on that same night which I posted elsewhere,but here it is again.It had a stretch on astrotoaster

I only used the RASA8 on 2 occasions for a number of reasons. It is on its way back to the US as we speak for adjustment of the mirror tilt which is probably more obvious on this image.

 

astrot 45x4 491.jpg

 

cheers

Paul



#21 lollywater

lollywater

    Sputnik

  • -----
  • Posts: 39
  • Joined: 10 Feb 2013
  • Loc: Bendigo Victoria Australia

Posted 12 February 2019 - 09:42 AM

Hello FWHM

They were all RASA8 and the 294. 

ngc 253 was a fits file saved at 1 minute on sharpcap and it was 137Mb file.nd the 15sec horsehead would have been a similar size. I would suspect trying to retrieve information after so much compression to jpeg would be very difficult. The 2 shorter exposures were unprocessed but the 45 sec horsehead was stretched on Astrotoaster. I dont do much on AS, just extend to a figure of 5-10

 

If you look at the 45 sec horsehead ,the stars at the bottom are little donuts and the ones at the top are pinpoint. To be honest ,for EAA ,I am reasonably happy with the result but an astrophotographer is not.

I posted this on IceInSpace in the Beginners Astrophotography a month ago  and it was suggested I get it adjusted.

  

This image of the tarantula 15sec x12  on the 294 demonstrates the initial major problem . It was taken while the mirror rattled and before I tightened the Allen screws

 

2070 15sec x12 250k.jpg

 

Because there was such a difference after tightening screws,I think returning it is good advice

 

cheers

Paul



#22 lollywater

lollywater

    Sputnik

  • -----
  • Posts: 39
  • Joined: 10 Feb 2013
  • Loc: Bendigo Victoria Australia

Posted 12 February 2019 - 09:57 AM

I set the autosave on sharpcap to either 1 minute or 3 minutes and then see what I can get in that time. That is not just with the RASA but with the other scopes as well.I add FR's to F/4 newtonians to get as fast as possible .Images are usually nothing to write home about . I put up with a lot of vignetting but I get images fairly quickly which is my main priority.

 

When I get the RASA back, I will be concentrating on what I can get in a maximum of 3 minutes preferably in 1 minute

cheers

Paul



#23 jprideaux

jprideaux

    Explorer 1

  • -----
  • topic starter
  • Posts: 68
  • Joined: 06 May 2018
  • Loc: Richmond, VA

Posted 12 February 2019 - 10:05 AM

lollywater and FWHM, wht mounts are you using with you Rasa 8?  I'm trying to determine reasonable options for EAA.



#24 FWHM

FWHM

    Lift Off

  • -----
  • Posts: 17
  • Joined: 10 Feb 2019

Posted 12 February 2019 - 10:12 AM

Hi Paul, thank you for the comments. after celestron adjust your primary, i think you will like it.

what is the backfocus of your 294 camera and did you purchase additional camera adapter?


Edited by FWHM, 12 February 2019 - 10:17 AM.


#25 FWHM

FWHM

    Lift Off

  • -----
  • Posts: 17
  • Joined: 10 Feb 2019

Posted 12 February 2019 - 10:42 AM

 i use a celestron evo alt-az mount. 

Rasa 8 comes with a losmandy bar, whereas my evo alt-az is a vixen bar scope.

Ken, at https://www.all-startelescope.com got me a vixen to losmandy adapter. I use my sct and rasa using the same mount.

 

 

also, Rasa 8 does not come with a star finder. I got the celestron starpointer finder

 

to install the starpointer finder follow the instructions in the rasa8 manual. It is easy.

rasa 8 manual link https://celestron-si...ng_Web Only.pdf

you also need m45 adapter if you use a ccd or cmos camera, unless your camera has exactly 25 mm backfocus.

 


Edited by FWHM, 12 February 2019 - 02:58 PM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics