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DIY 'Mini observatory' setup recommendations

Astrometry Beginner Astrophotography DSO Reflector Refractor
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#1 Ayaan Hashim

Ayaan Hashim

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Posted 09 June 2021 - 05:44 AM

Hello,

This is my first post on CN. I have been interested in astronomy since I was six. I got interested in early 2020(I was 11 at the time) when I attended a stargazing camp(Bortle 4-5 skies) some distance from the city. There were 2 10inch dobsonians(I think skywatcher ones) at the site and a 6inch newtonian(for Deep Sky Object imaging) on a (I think CEM60). It sparked major interest in astronomy for me. Then when the lockdown began, I began looking at the skies for stars, and I began astrophotography with an Canon SX40HS fixed lens camera(pretty small sensor-but hey, its a fixed lens camera anyways). The camera is presently broken(bought around 2012). I have a powerseeker 60eq (60mm focal ratio:-15 uncoated optics, doublet achromatic refractor) which I use for stargazing(no DSLR or mirrorless for prime focus imaging, sadlyfrown.gif ). I have been researching on the web and books about astronomy, but you can call me a beginner. Of course, possibly like else I want that 10 micron gm2000hps Combi and a (possibly not so well known) 12" Lacerta Photonewton+an ASI2600MM, but I have no experience with these kind of high-end mounts, a newtonian with an Octo60 focuser, and a camera with a PEAK QE of about 90%. Anyway, I'm Thirteen years oldgrin.gif, and the budget makes the wallet go boom . So I was thinking if I could make a rig primarily for collecting scientific data(Okay, I like astrophotography, but I like astronomy better). The present budget(USD $60wink.gif ) still doesn't allow it, but I'm still interested. The main objectives:-

1.Detecting exoplanets(are 14bit+ sensors required?-I know even 12bit will do in some cases)

2.Detecting NEOs(I know aperture is key here-imaging object as faint as 16th magnitude-possibly even 18th mag.=get that huge mirror!)

3.Imaging the faint fuzzies(Light pollution to deal with)

4.Monitoring asteroids and comets

5.Photometry of variable stars

6.Spectroscopy(Is this possible? And anyways, a good spectrograph will blow the bank sky-high-but still want to do it)

7.Discovering supernovae, novae and asteroids

8.Taking images of what seems like an empty field in the sky(relatively small FOV), hoarding hours of data on that patch of the sky, and revealing faint objects- it just seems interesting to analyse those fields.(Essentially imitating Hubble from a certain perspective)

Thats the lot

Now speaking of the equipment, I love DIY projects. I've been fixing old RC cars(okay-quite simple to dolol.gif  ), constructing a fan(easy peasy-anybody could do itwink.gif ), and have rebuilt RC cars after taking them apart(All right, all right, I heard you-that's quite simple toolol.gif ), etc.

I am not unaware of the steep learning curve. I haven't had an experience in guiding, using a mount, or using a dedicated, cooled astronomy camera. Usually people here say that a beginner should buy an heq5(Generic Orion Sirius EQ-G or an eq6r pro(Generic Orion Atlas II), with a 80mm refractor and a DSLR/mirrorless camera and learn it that way, eventually starting to guide before buying that C9.25. I would like to hear people's comments here on learning astrophotography with a setup like the one described below

Now for the equipment(mostly DIY)-

The mount-

I want to build a DIY EQUATORIAL FORK goto mount with encoders on both axes(preferably 22bit resolutionsmile.gif ). I would like it if it is capable of carrying a 10" newtonian(and accessories- I think the weight isn't going to exceed 30kg) about 1m long without much difficulty. And yes-there is the debate on which to use-SERVOS OR STEPPERS-I prefer servos as the have higher resolution than steppers-but I am also aware that if they make the scope collide with something(like the pier or tripod)while tracking or slewing, the servos will burn out, or until they do keep pushing the scope until it breaks evillaugh.gif . Steppers are cheaper, will stop if the scope encounters an obstruction when tracking or slewing and not burn out, but have much lower resolution usually about 1,9 degrees, sometimes 0.9 degrees-and microstepping doesn't help much-decreases the amount of load it can carry, and actually decreases the accuracy too. The solution-Use gears-but then-backlash/binding?(periodic error too)-okay, fine get a belt-I prefer a direct drive system. I would like it if the system allowed a slew speed of more than 20 degrees per second-but  it might might cause the primary mirror of the telescope to move-but then I have the option of satellite tracking-But not really interested much in that. The accuracy?-Pixel scale=not yet confirmed- I actually would like it if it had an RMS of less than 0.5 arcseconds in normal/average seeing conditions. Software-PHD2 or Metaguide?

The optics-

The main newtonian astrograph:-

I did some research on this and people here seem to be saying the best optical mirrors available on the commercial market are made by Zambuto mirrors. Excellent contrast, good Strehl rating, and overall excellent performance. I'm looking at the 8" f4.5, the 10" f4.5, and the 11" f4.5. They seem to be good ones for the price. Now the secondary mirror-Antares secondary elliptical mirrors? And which size ?And how am I going to correct the coma if there is any at f4.5? Collimation?

The refractor:-

It would be great if I had a refractor piggybacking on the reflector to do widefield imaging at the same time, and also to confirm my observations.

I would like to make a good apochromat here with no less than 4 inches of aperture-preferably 5 inches-but the question arises-Where am I going to get the lenses from? Edmund Optics? The field flattener?

Guiding-Off Axis Guider?

The camera:-

Have absolutely no idea. Could get a ZWO, Atik, or a QHY, and KAF chips(Used in the SBIGs) are out there too, but they seem to be outdated.

Can I somehow modify SBIG's AO to fit to the telescope and chip?

The program or the mount-

I used to like stepper motors but after doing more research on servos, servos seem the way to go. I like onstep, but it seems to be compatible with steppers only. I can write my own program, similar to onstep, but it can accommodate servos. If I can can centre the main code around a Raspberry Pi4b, It can be possible to make it a standalone system with a DIY joystick and hand controller. With some python and C, it might be possible to make the thing a fully automated system which selects targets on its own each night when I don't have the time to operate it. Budget-<$3000. Is this all possible with a setup like this operated by a beginner

Any thoughts and comments would be appreciatedflowerred.gif

Thanks in advance,

clear skies,

Ayaan


Edited by Ayaan Hashim, 09 June 2021 - 07:01 AM.

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#2 Mark Lovik

Mark Lovik

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Posted 09 June 2021 - 09:59 AM

Building from scratch can be fun ... but will take considerable time.

I was going to take a similar route, but took some valuable shortcuts.

 

How about getting a small reference system running first.

- EQMOD, OnStep sort of thing.  Retrofit an existing mount or build something small first.  It should be easier to prototype when it is small.

- Start with a small refractor 72-80mm (Refractor, or APO depending on your goals)

- Start simple for imaging (mono or an existing camera)

 

Use this minimal system to learn.  The learning curve will still be high when you are not using an off the shelf system.  Then use this to find out what you want for the next step.



#3 Ayaan Hashim

Ayaan Hashim

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Posted 09 June 2021 - 11:25 PM

Hi Mark,
Thank you for replying to my post here on this wonderful forum. I know that it will take at least about two months to put together(Which includes greasing and tuning the mount if it has problems and is not a direct drive system), and also aligning the optics well. So well, about a year ago I stumbled this site called Tejraj. I think it offers GSO mirrors for a pretty reasonable price. An 8" Quartz comes for about $180USD. It states on the site that GSO mirrors are 1/12th wave but I suspect that is the RMS. I think the actual wavefront is about 1/6th wave, which is still pretty decent. Guang Sheng Optical has a relatively affordable price for their mirrors, including a monster 16" f4.5(Okay, there are still much bigger mirrors on the market) which comes for about the cost of an HEQ5($1,150 USD). I've heard the quality of their mirrors varies...have read somewhere on CN that experienced amateurs mistook a GSO 16" f4.5 mirror for a Zambuto one...here- https://www.cloudyni...-16-f45-of-gso/ .
So my new plan-
get -
1.A GSO quartz mirror, an 8" f6. Why? Because all the other 8" mirrors have been sold out. And this Quartz one cools much quicker than a Pyrex one. But I'll still be using a computer cooling fan(low vibration, low noise)
2.Yaskawa SGMCS motors(high torque, high resolution ones) for the fork mount to make a direct drive system?
3.An elliptical secondary. Which one? A GSO from Tejraj?
4.The camera-An ASI 183MM cooled? But there is amp glow-and small pixels not ideal when imaging at a focal length of 1200mm for a beginner...ASI 224MC with peltier mod for EAA?

5.The reducer-I really don't know which one to get...if I get a 0.5x GSO one...then I can turn the newt into a deep sky astrograph at f3.0...Paracorr required?...demands of tracking on the mount reduced
6.Coma corrector-Parabolic mirror...which one?
7.Some spectral grating
8.A focuser...which one...an octo60?
9.Hybrid ceramic ball bearings...install them on both axes and lubricate with lithium grease(Aeroshell 33)
10.Autoguiding system-ASI 290mm woth an OAG?
Will this all work?
I guess with the reducer this will (sort of) mimic an 100mm refractor at f7.5 or f6.
And the deep field thing...-huge demand on the mount if used with a powermate
Hope this also can also work for a beginner...or just get a 120mm f5 Orion doublet and hitch it on an AZ GTI in equatorial mode for learning astrophotography and EAA?(I know the mount is getting overloaded here)

Edited by Ayaan Hashim, 10 June 2021 - 08:59 PM.


#4 Ayaan Hashim

Ayaan Hashim

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Posted 10 June 2021 - 11:50 PM

Maybe I should just blow the greenbacks on a K1 ii with ASTROTRACER.




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