Auto-guided EQ1 mount

themos · July 25, 2012

Well, finally got the autoguided EQ1 out again last night! Polar alignment software said about 3 arcminutes error (after 8 iterations). I used a cheap Zeiss 135mm "f/3.5" lens stopped down to f/5.6 and the EOS 450D with the Astronomik CLS filter. A quick stack of 10 3-min ISO 400 shots of the Veil nebula area (no calibration frames), the full frame and a 100% crop:

And this is a 100% crop of 7 6-min shots showing some star elongation due to inadequate tracking.

Gina · July 25, 2012

The Cygnus Loop is a difficult one - very faint and swamped by other stars of the Milky Way. But you've caught it there - well done

themos · September 4, 2012

I tried a new approach last night: drift alignment with EQAlign instead of the photographic/astrometry method.

EQAlign gave me some trouble recognising the guiding webcam (a SPC880NC flashed to SPC900NC and modified for LX, although I didn't use the LX features). I was using the finderscope for this. There doesn't seem to be a way to access the camera dialogs from EQAlign, so I had to use SharpCap to set the camera parameters to something usable and then switch to EQAlign.

Once I had Altair on the EQAlign screen everything went smoothly from there on. First you do the calibration step for determining the RA direction relative to the image frame. Then you do the drift alignment. The first time I let it run for about 4 minutes as I knew that there would be a lot of correction (I originally aligned by just eyeballing Polaris).

I was only doing the Azimuth correction as I was intending to image the South equator as a test anyway and I don't think the Elevation correction is needed for that. EQAlign's first recommended correction was a large one, taking 4 iterations of slewing followed by mount nudging. I used the RA motor to slew in RA and a slow-motion control for DEC. You are asked to put your star in the red circle (by RA/DEC movements) and then move the mount to place the star in the green circle, simples!

I then let it drift align again for 10 minutes, after which the new correction was "32" (is that arcseconds or pixels?), taking 2 iterations. Did that, then let it run another 10 minutes and I was bang on: correction was "1". That didn't take too long, I thought. I took a few 5 minute shots, wide open at f/3.5 with the old Zeiss 135mm lens, at ISO 400 (giving me about 8 arcseconds to the pixel), autoguided with PHD. They turned out remarkably well. I like knowing I have another method to fall back on if the photo/astrometry method doesn't deliver the goods.

Here is a 100% 300x300 crop of one of the frames, all 6 were same quality.

JamesF · September 4, 2012

I'd say that's pretty good. The stars look beautifully round as far as I can tell.

James

themos · September 4, 2012

annotated crop

themos · September 4, 2012

The more I gain confidence with the autoguided EQ1, the more it makes sense to spend money on some expensive glass...I've already saved myself the cost of an Astrotrac...

themos · September 4, 2012

Well, I've gone and done it now... hope that 200mm f/2.8L turns up soon. Meanwhile, trying again tonight more tests with the EQ1. Polar aligning is taking a longer time today. I will soon have the Azimuth nailed and then I will try the Elevation correction. I am using the older laptop with the parallel port for the LX webcam.

JamesF · September 4, 2012

Having the same lens myself, I'm intrigued to see how you get on.

James

themos · September 4, 2012

I just hope there are lots of nice targets for that focal length, especially from the Mediterranean where I hope to be taking the setup.

Gonzo · September 5, 2012

The more I gain confidence with the autoguided EQ1, the more it makes sense to spend money on some expensive glass...I've already saved myself the cost of an Astrotrac...

I got my eyes on some Voigtlander lenses for my GF1.

It's time I dust off my EQ1 platform and start taking pictures again.

This little project I believe is fully complete, not sure what else can be added to it to be honest.

Nice work on the recent pictures Themos.

themos · September 5, 2012

I don't know, Gonzo, I am still not convinced that the EQ1 can prove stable enough for reliable imaging. Sometimes it feels like you've nailed the Polar Alignment and then you get the odd trailed image, especially if you move to a different part of sky. I am taking 5 min exposures now of the Sadr neighbourhood (with the Zeiss 135mm f/3.5) and so far so good. I used drift alignment today again and it sure takes a lot more time. Hopefully I will get to play with the 200mm f/2.8 tomorrow. Anyway, the more imaging runs the more confidence I have that it will behave when I take it abroad on holiday to some darker skies.

themos · September 6, 2012

This is from last night, 1h 20min, 5min subs, ISO400, not too bad, especially with the f/3.5 lens wide open.

Gonzo · September 7, 2012

I use my EQ1 on my DIY build window platform, the all thing is locked down to the window ledge and will not bulge, I can move the camera or point the EQ1 to almost wherever I want without loosing the polar alignment.

One way to see it is that as a portable little mount for widefield photography, it's hard to beat (that's unless you're loaded and can afford an Astrotrac...)

themos · September 20, 2012

I thought we should have a link to this thread from here as it really solves the problem of not having GoTo on the EQ1. Since we already do plate-solving for polar alignment, why not do plate-solving for finding targets? And do it with Stellarium as the interface!

http://stargazerslounge.com/topic/143540-star-hopping-with-on-the-fly-astrometry/

themos · September 20, 2012

More experience with autoguided EQ1, 450D, 200mm lens, 2 minute subs. http://www.astrobin.com/20453/

themos · September 20, 2012

According to the observed declination drift (via PHD Log files) of 20 arcseconds over 30 minutes at declination +30degrees, the polar alignment was within 3 arcminutes. The PHD log file also gave an RMS error in RA guiding of 1.5 arcseconds. As this was with the much heavier (760g) 200mm lens and in a bit of a breeze, I think this was a success.

Gonzo · September 20, 2012

I do like that a lot, will be reading it later on in full.

I thought we should have a link to this thread from here as it really solves the problem of not having GoTo on the EQ1. Since we already do plate-solving for polar alignment, why not do plate-solving for finding targets? And do it with Stellarium as the interface!
http://stargazerslou...fly-astrometry/

Scotty600 · October 21, 2012

attachment

Hard to believe that can be done with an EQ-1.....nice job!

Gonzo · October 21, 2012

It just shows that you do not have to spend lots of money on very expensive kit to achieve modest results.

themos · October 22, 2012

Finished my twin dew heaters over the rainy weekend, ready for clear skies and I have a good target in mind that will be just right for 200mm.

bamus · September 2, 2013

This is a joined project with Themos about the auto-guided EQ1.
In no particular order some threads to help you understand the behind of this project,
eq-polar-alignment - Rosedale Photo Polar Alignment - Google Project Hosting
http://www.store.sho....com/eq_mod.pdf
http://stargazerslou...l-i-manage.html
http://stargazerslou...uider-mkii.html
http://stargazerslou...syes-style.html
BIG thank you to everyone involved in the above links.

hi Gonzo

I plan to buy and make eq1 autoguide. I have got few questions.

- link to shoestring describes eq3 and eq5 modification. Is it same process for eq1? any major differences?

- how and where do you attach Arduino

- what is code you have used to program Arduino

I would appreciate your replay. Thank you in advance!

themos · September 2, 2013

The process is the same. The Arduino has a USB interface to your control computer and will also have a number of wires connecting it to the hand controller (I use 3 wires: RA+, RA- and GND). See pics in

http://stargazerslounge.com/gallery/image/11077-eq1-multispeed-controller-mod-1remove-screws-4-1-buttons/

The arduino code is in a file provided with my installer

https://docs.google....dit?usp=sharing

Once you install the ASCOM driver with the installer, you will find the Arduino "sketch" in a .pde file.

bamus · September 3, 2013

thanks themos.

Will have a look into this in the eveninig. Not sure if I will manage to do this mod, but I least I will give it a go. If I will stuck at some stage I will have to ask questions here.

Gonzo · September 3, 2013

thanks themos.
Will have a look into this in the eveninig. Not sure if I will manage to do this mod, but I least I will give it a go. If I will stuck at some stage I will have to ask questions here.

It's an easy mod to do, just a little bit fiddly...

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Auto-guided EQ1 mount

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