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Low budget build in progress...

EAA equipment reflector
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#1 Relativist

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Posted 23 November 2017 - 12:17 AM

As noted in my Low-low budget build thread it was mentioned that my 6" f/4 imaging newt would likely fit on the Nexstar 6/8 SE mount. This was confirmed in that thread. Well as luck would have it someone wanted the OTA only from a Nexstar 6 SE and I was able to purchase the mount only from Mike at OC Telescopes.

 

This is great news as I can now use both my NexSky224 (the 100mm f/4 Skyscanner with Nexstar mount and RI 224 camera) and this new setup with the A7s at the same time.

 

I'll say this though, the ~4" f/4 NexSky224 feels much much lighter than the 6" f/4. That said, the 6" with it's 2" focuser is going to be a nice wide field setup with the A7s.

 

The other comparison I'm interested in studying is the 6" at f/4 and the 12" at f/2 (same focal length) and different pixel sizes.

 

This just leaves my 8" without a mount, I'm planning on an AVX eventually for it.

 

Anyway, on the the pictures!

 

IMG_2078.jpg

 

IMG_2082.jpg


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#2 Relativist

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Posted 23 November 2017 - 12:58 AM

Here are a few places to get a 6" f/4:

 

https://www.astronom...ube_p18868.aspx

 

https://octelescope....nian-ota-os-6in

 

The Nexstar 6/8 SE mount is often on the used market, but also let your local scope shop know if your looking for one as people often want the OTA only. (assuming your lucky enough to have one of those around)

 

As for what camera I'm paring the 6" f/4 with, I don't know as of yet, but I'm thinking that most times I'll use it is when I want to get a quick look at the sky with my A7s.

 

The interesting thing about the 6" f/4 when it's paired with an ICX811 camera the light flux per pixel will be very close to what is provided by a 4" f/4 when it's paired with an IMX224, So I might end up assigning my revolution imager 1 camera to the 6" f/4 on a permanent basis. Likewise I'm considering an IMX385 for the 6" f/4 as well since it will give a close FOV to the 4" f/4 with the 1/3" format 224.

 

Here is a screen shot of the calculated FOV difference overlaid on the Pleiades.

 

Screen Shot 2017-11-22 at 10.04.15 PM.png



#3 CA Curtis 17

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Posted 23 November 2017 - 04:53 PM

Curtis,

 

Does you 6" Newt clear the mount at zenith?  I wouldn't think it does and doesn't look like it from the pictures.

 

Regards,

Curtis



#4 Relativist

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Posted 23 November 2017 - 05:55 PM

Yes it does! Remember the AT6IN/6"TPO has a longer tube than is required, so the balance is rearward. I'll take a picture when I get a chance.



#5 Relativist

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Posted 23 November 2017 - 11:27 PM

Clears just fine, plenty of room.

 

IMG_2083.jpg


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#6 Rickster

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Posted 24 November 2017 - 10:41 PM

Nice rig Curtis.  I am glad to see that someone else will be giving an AT6IN a chance.  I have gotten countless hours of enjoyment from mine.  These little scopes are so compact that they are easily adapted to a number of mounts.  For a while, I had mine mounted to an old Meade LX3 8" SCT fork mount.  These regularly come up for sale for ~$100.  To give an idea of what the AT6IN is capable of, I am attaching an EAA image of the Rosette nebula that I got using an AT6IN, a Canon T4i, an LX3 mount and AT/DSS.

Attached Thumbnails

  • Screenshot (1) resized.jpg

Edited by Rickster, 24 November 2017 - 10:43 PM.

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#7 Relativist

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Posted 24 November 2017 - 11:20 PM

Thanks for the example Rick. I'm still thinking about what camera to pair it with, although like I said it might be the A7s portable rig, I'm considering a dedicated camera. Maybe an IMX385 based camera?



#8 Rickster

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Posted 25 November 2017 - 02:02 PM

I decided to use a DSLR because the AT6IN has an edge on most other scopes when it comes to imaging large colorful nebula.  That is, the reflector design is color neutral and the fast optics provide a wide field of view.  And since this is to be a budget build, used DSLRs provide a lot of value for the $.  A used T3i would be a nice budget minded match.  Or for a little more money, a used T4i adds a swivel screen and higher iso capability.

 

If you want very wide views such as would be provided by your A7, the AT6IN would benefit from a coma corrector.  I experienced coma in the outer/rectangular portions of the APS-C sensor of the Canon T4i.  This is not a serious problem in that the image can be cropped and still retain a wider field of view than most Astro cameras.  I considered the coma affected area to be a bonus to be used for locating objects.  Once I got the object centered, I normally cropped my images to be square.  That left some coma in the corners.  The rigorous astrophotography guys would probably object, but I didn't find it objectionable for EAA.   And even the cropped image has a very wide field of view as shown in the image of the Rosette nebula, which is a large object (1.3 degrees). 

 

I want to be clear that the coma in a AT6IN is not a fault of the scope.  It is an unavoidable consequence of the laws of optics for fast reflectors.  You can get fast reflectors that have reduced coma, but these are very expensive and incorporate a factory coma corrector.  In the case of the AT6IN, the coma corrector doesn't come with the scope, but can be bought separately.  I used mine without a coma corrector.



#9 Relativist

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Posted 25 November 2017 - 03:12 PM

Agreed on coma correction for these Imaging Newts. When I used the A7s with my 8" f/4 initially, i found that if I simply used the APS-C crop mode the coma at the edge was barely noticeable.

#10 Relativist

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Posted 27 November 2017 - 01:11 PM

Second question, so besides selecting a dedicated camera, I'd also like to select a computing solution. I figure if I go with an HD resolution camera like the IMX 385 based cameras then I'm using Sharpcap/AT (unless SC is good enough by then) and can live with the same compute stick I have on the 100mm/224. But if I go with something larger and higher resolution then I think I need more compute power. I'm considering the next most powerful compute stick that comes preloaded with windows 10. Does anyone have experience with that model and running a 5 - 16 megapixel camera? If I did get the 294 I'd likely be using bin 2 and superpixels, but I'd like the compute portion of the system to be able to handle the full camera resolution if called upon.

#11 Robrj

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Posted 28 November 2017 - 06:02 PM

I looked at benchmark sites when I was considering an M3 stick (I don't know how reliable the benchmark sites are). For the M3 processor, it benchmarked slightly less powerful than an i3. The only issue with them is 2 of the 3 USB ports are on the power block.

If you already have one though, I'd try the Computestick gen 2. I've had a lot of stuff running on mine. I've collected with both Sharpcap and Starlight Live simultaneously with mine (Ultrastar & ASI185MC). I know Hiten uses it with his ASI294MC but I think he bins. You might ask him to give it a shot to see how it performs.

#12 Robrj

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Posted 28 November 2017 - 07:18 PM

CityObserver uses an M3 with an ASI294MC at full resolution. He said no problems:
https://www.cloudyni...ults/?p=8223955
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#13 Relativist

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Posted 28 November 2017 - 09:02 PM

CityObserver uses an M3 with an ASI294MC at full resolution. He said no problems:
https://www.cloudyni...ults/?p=8223955


Thanks, I hadn't caught that detail. The CS325 model already has windows 10 loaded, so looks like a great deal.


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