14 replies to this topic

[UB_Astro]

I just have some progress with my EAA activity and would like to introduce my Ultra Basic EAA setup.  I hope to practice EAA with the minimal investment, knowing that there will be compromises.

 

Essentially my EAA setup is divided into 2 modules: The imaging module and the tracker module (photos enclosed).  They are standalone modules.

 

For the imaging module, the lens is a DIY refractor.  I took the main lens out of a old Celestron 7x50 Binoculars and connected it with some PVC pipes.  The focal length is 180mm, so f/3.6.  The camera is a Raspberry Pi HQ camera, using a Sony IMX477 sensor.  Resolution is 4056x3040 max and pixel size 1.55um.  This camera must be used with a Raspberry Pi, which happens to be a Pi 3B+ in this case.  I also use a HDMI adapter board so the connection between the camera to the Pi is via a robust HDMI cable, not a delicate flexible flat cable.  Apart from controlling the camera, the Pi 3B+ also perform live stacking using ASTAP.  Some python scripts are used to execute all the functions and provide a user interface.  The Pi 3B+ also serves as a WiFi hotspot so I can connect a smartphone via some remote desktop app to control Pi and view the results.  The whole module is powered by a 5V mobile power pack.

 

The tracker module is built around a normal EQ mount which I acquired from second hand source.  I add a stepper motor to the RA axis for tracking while the rest are still manually adjusted.  The stepper motor is driven by a Arduino using a very simple script (just straight 1 speed stepping, no fast forward whatsoever).  The power supply is a 12V lead acid battery which power the stepper motor directly and also drive a 5V regulator for the Arduino.  The tracker works completely independent of the imaging module and there is no communication between them.

 

A smartphone is used as the overall control.  Preview for locating the target, execute the capture commond when target found, then view the live stack results.

 

As the Pi 3B+ is not powerful, the images are captured with a 2x2 binning down to 2028x1520 and in PNG format.  File size is about 3M each sub.  From the advice of Han (author of ASTAP), the image need to be further bin down 2x to achieve successful alignment for live stacking.

 

I use 4s per sub as a base and capture about 40 subs for 1 target.  The trial last evening was rather successful.  I "observed" 3 DSOs, taking total 120 subs and all stack successfully.  100%.  I live in big city with Borte 8/9 sky and EAA is really helping me out.

 

I have enclosed the live stack images of the 3 DSOs.  Each are live stack output of 40x4s, with UHC filter installed.  The targets are M31, M103, NGC889.  The optics are quite bad though.

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[UB_Astro]

Live stacked images

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[jimhoward999]

You might consider using a low cost guide scope as your imaging module.  For example a Svbony SV106 50mm F/4 guide scope only costs $80.  It has good image quality, includes a helical focuser, and would lend it self to mounting your sensor module with an adapter.  Other guide scopes or low-end achromatic refractors would work as well.  The Svbony one is just quite cheap.

 

I think you will have trouble getting adequate image quality from a scavenged binocular objective....if for no other reason because the binocular objective is designed to be used with the glass path of a porro or roof prism, which is absent from your optical train.

[UB_Astro]

Thanks for the advice.  Yes the quality of the images from the binocular lens are bad, with a very big abbrevation in the Red colour.  I am planning to test another telescope that I have on hand, which is a cheap but surprising decent Maksutov Cassegrain with 60mm aperture and 750mm focal length.  It is being marketed with different names like Sarblue60, Maksy60, Acuter60 etc.  I intend to try this with a Svbony 0.5x focal reducer in the coming days to see how it works.  I have used it for some astrophotography before.  Quality is decent except that the 0.5x focal reducer brings coma.  I think eventually I will need 2 lens to cover the observation target range, one with a 1.5 degree FOV and one with a <1 degree FOV.  Have thought about the guidescopes before but I will test out the Mak first to see how it goes.

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[alphatripleplus]

The trouble with using Maks for EAA (and I started with one) is that they are natively very slow - yours looks like it is about f/12.5, which is about the same f/ratio as the SW 102mm Mak that I started with. It is hard to get enough focal reduction to make image acquisition fast enough with a slow Mak for DSOs and not get bad aberrations, even with a small sensor. I moved on to SCTs with reducers  after my experiments with the Mak.

[UB_Astro]

Add a new member to the image capture module a week ago.  This is a DIY reflector, 76mm aperture 300mm focal length (f/4).  A ultra low profile focuser is made to enable focus with the Raspberry Pi HQ Camera.  To reduce the imperfections of the spherical mirror an aperture mask of 60mm (concentric to the OTA) is placed in front of the OTA.  This trades image quality with aperture.  After a few trial, this might well be the principal lens for my EAA activities.  Attached a EAA image of M103 captured this evening.  5s per frame and this is a live stack of 42 frames.  Only black point adjusted, a simple stretch and cropped to cut the edges.  No other post processing.  Clouds just came so quickly and I could not take more.

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[steveincolo]

That’s interesting.  A couple questions.  Have you tried it without the aperture mask?  The aperture mask makes it a slower scope, and the camera you’re using is smallish, so the optical issues from a spherical mirror might not matter as much.  What software are you using to align, stack, and adjust the subs? Edit: oh I see, per your initial post, you’re using ASTAP. 

Edited by steveincolo, 07 December 2022 - 01:56 PM.

[mgCatskills]

Wow, I wish I were as handy as you are!  Unfortunately, my own DIY projects are pretty much a disaster.  I'm uber proud of having converted an obsolete 12 V multi-camera video power supply to the thing that powers my telescope accessories but two or three other attempts have failed miserably.  So I have little direct experience to share.

 

Mediated experience may be another story.  Have you watched Astrobiscuit on YouTube, or gone to his website?  He does a lot of programming around how to make inexpensive telescopes work, or modernizing old scopes, etc.  He runs a discord server filled with like minded "nerds" who do this stuff...and who can make custom 3-D printed parts, etc.  Maybe a useful community to tap into.

 

https://astrobiscuit.com/

 

Also, he's very funny.  His head to head battle with Stellina on YouTube is LOL. 

 

Michael

Edited by mgCatskills, 07 December 2022 - 05:46 PM.

[UB_Astro]

That’s interesting.  A couple questions.  Have you tried it without the aperture mask?  The aperture mask makes it a slower scope, and the camera you’re using is smallish, so the optical issues from a spherical mirror might not matter as much.  What software are you using to align, stack, and adjust the subs? Edit: oh I see, per your initial post, you’re using ASTAP. 

I tried several configurations: no mask, a 66mm mask and this 60mm mask.  Difference is obvious.  I do try to assess the FWHM values.  For no mask and 66mm mask, the avg FWHM values are in the range of 6-7, while the 60mm mask gives something around 3-4.  Yes the mask will slow down the scope a bit but I think it is still OK for me.

 

Yes, the plate solve, align and live stack are all done with ASTAP.  This is the only one that I find which works on Raspberry Pi and handle non RAW file formats.

[UB_Astro]

Wow, I wish I were as handy as you are!  Unfortunately, my own DIY projects are pretty much a disaster.  I'm uber proud of having converted an obsolete 12 V multi-camera video power supply to the thing that powers my telescope accessories but two or three other attempts have failed miserably.  So I have little direct experience to share.

 

Mediated experience may be another story.  Have you watched Astrobiscuit on YouTube, or gone to his website?  He does a lot of programming around how to make inexpensive telescopes work, or modernizing old scopes, etc.  He runs a discord server filled with like minded "nerds" who do this stuff...and who can make custom 3-D printed parts, etc.  Maybe a useful community to tap into.

 

https://astrobiscuit.com/

 

Also, he's very funny.  His head to head battle with Stellina on YouTube is LOL. 

 

Michael

Thanks, I did watch some of his video.  Very funny guy.

[UB_Astro]

Do some EAA live stacking this evening using the DIY reflector.  M42 -  100x3s.

M43 is just starting to be visible.

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[UB_Astro]

Also tried M1. 150s3s.  The resolving power is clearly not capable in this case.

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[wykbbb]

Are the 3 second subs a limitation of your budget DIY EQ mount? Would longer subs help your images? I can get 5-10 subs on AZ-GTI in alt-az mode.

Edited by wykbbb, 14 January 2023 - 06:11 PM.

[UB_Astro]

Are the 3 second subs a limitation of your budget DIY EQ mount? Would longer subs help your images? I can get 5-10 subs on AZ-GTI in alt-az mode.

You are right on the spot.  I've been fighting this for a long time.  The issue is I see a random significant "periodic" shift along the RA direction.  The amount of shift can be + or - 0.5 degree over a short period of time.  I tried cleaning up and re-lubricating the worm gear.  Then I intentionally do not maintain a balanced counterweight to ensure the gear is always pressing on 1 side.  Not successful.  I believe it is the GT2 timing belt/pulley might the source of the problem.  I cannot judge if these low cost stuffs from Amazon is manufactured accurately teeth by teeth.

 

Still for EAA I think I can live with rather short exposure time.  I aim for a quick show up of the target which I do not have any chance to do visual observation.  I live in big city with Bortle 8, if not 9, sky.

[wykbbb]

You are right on the spot.  I've been fighting this for a long time.  The issue is I see a random significant "periodic" shift along the RA direction.  The amount of shift can be + or - 0.5 degree over a short period of time.  I tried cleaning up and re-lubricating the worm gear.  Then I intentionally do not maintain a balanced counterweight to ensure the gear is always pressing on 1 side.  Not successful.  I believe it is the GT2 timing belt/pulley might the source of the problem.  I cannot judge if these low cost stuffs from Amazon is manufactured accurately teeth by teeth.

 

Still for EAA I think I can live with rather short exposure time.  I aim for a quick show up of the target which I do not have any chance to do visual observation.  I live in big city with Bortle 8, if not 9, sky.

Short subs are fine with EAA. I was just surprised that you could only get 3-4 seconds on an eq mount. The reason some people get an eq mount instead of alt-az mount  for EAA is to get longer subs. I think  improving the mount would be the next logical step. 

Edited by wykbbb, 15 January 2023 - 02:18 PM.