AZ SynScan GoTo mount for astrophotography

[Aetherum]

Hi there!

 

I recently acquired an AZ SynScan GoTo mount to replace my AZ3 to do some astrophotography with an eyepiece adapter and a T2 ring. I'm still waiting on my battery to arrive, so I haven't been able to test it yet. But in awaiting the necessary accessories I starting looking up some information and I found that these mounts are not usable for astrophotography at all. Now, the issue at stake here is whether the vibrations of the motor would interfere with smooth tracking for high exposure times, and whether there are any practical solutions to eliminate said vibrations to any degree. Does anyone have experience with said issues or should I just go ahead and look for an equatorial mount? I thank dearly for advice of any kind!

 

Let the skies be clear.

[KP82]

AZ mounts are not suitable for long exposure astrophotography because they cause field rotation. It has nothing to do with the vibration of the motor.

If you're preparing to get into long exposure astrophotography, an EQ mount is a must. Some AZ mounts can be converted into EQ mode with the help of a wedge (e.g. AZ GTi), but I'm afraid that's not possible with your AZ Synscan.

[Aetherum]

KP82, I wasn't aware that AZ mounts are prone to field rotation, but that makes a lot of sense. But I suppose the exposures can still be longer then without a tracking mount, at least? I don't know how that would translate in practice. 

[Cosmic Geoff]

All is not lost - with an AZ GoTo mount, a small telescope, a suitable camera and a laptop, you can take shots of a few seconds, single or live-stacked, of various objects, to extend the capabilities of your telescope. See the EVAA section here.

[Aetherum]

I use a D3300 and I ordered a WiFi adapter to computerise my mount. And thank you, I'll look into it!

[rotatux]

AP with AZ tracking mounts has proved to be possible within certain limits and constraints, typ. with 20s-60s subs.

See / Search the (huge) thread here : 

for examples, techniques and general advice.

[Aetherum]

8 minutes ago, rotatux said:

AP with AZ tracking mounts has proved to be possible within certain limits and constraints, typ. with 20s-60s subs.

See / Search the (huge) thread here : 

for examples, techniques and general advice.

Cool! Thank you, quite interesting thread. 

[maxchess]

You don't mention what lens/scope you have. If you are imaging on an AZ mount with a DSLR then you should concentrate on widefield targets using a focal length less than 200mm, which will tolerate less good tracking.  Also ramp up your ISO.  On targets like M31 etc you can get acceptable results with loads of 10 sec or less exposures.  But in the end there is no substitute for an EQ mount if you want to get into imaging.

[Aetherum]

12 minutes ago, maxchess said:

You don't mention what lens/scope you have. If you are imaging on an AZ mount with a DSLR then you should concentrate on widefield targets using a focal length less than 200mm, which will tolerate less good tracking.  Also ramp up your ISO.  On targets like M31 etc you can get acceptable results with loads of 10 sec or less exposures.  But in the end there is no substitute for an EQ mount if you want to get into imaging.

I have a ST102 achromat, so 102/500 with various eyepieces. I have an ST80 as well, because that is the scope I bought originally, the ST102 came with the mount, but I will be selling it since the ST102 is just a better scope. I also have a cool vintage 10-1000 Russian Maksutov-Cassegrain lens, but that one isn't of much use for wide-field imaging. 

[maxchess]

All a bit on the long side for a AZ mount. Do you have a telephoto for the DSLR?

 

[Aetherum]

3 minutes ago, maxchess said:

All a bit on the long side for a AZ mount. Do you have a telephoto for the DSLR?

 

I thought fast refractors with an f-stop until about f/5 were perfectly ideal for imaging purposes? I have a kit lens with the D3300 going from 18 mm to 105, but at 105 the aperture is at 5.6. 

[maxchess]

Yes a refractor at f5 or even f6 or 7 is ideal on the right mount. With an AZ mount Its the focal length you need to think about. The longer the focal length the more critical the tracking. Conversely the shorter the focal length the more forgiving it is. At the extreme you can take a 20 sec exposure of the milky way with a 24 mm lens on a static tripod.  The smaller f number tells you how much light is let in during that period so a faster lens allows you to get better results for a given exposure time.   So your 105mm lens is worth a try. 

[Aetherum]

Yes, I see how important the mount is in this case. But as said, I hadn't accounted for field rotation. Especially because my neighbor, which is an experienced astronomer, hadn't mentioned anything about it when I asked him about the mount. I know how aperture in terms of f-stops work. My 10.5 mm fisheye lens is an f/2.8, so that would gain some great results if I get the chance to shoot at a great location again. I'll just see what I can get with this, my camera is currently limited to 30-second exposures anyway. Thank you for your advice.

[Cosmic Geoff]

Aetherum - check this section to see what I imaged with the same 102mm achro scope as yours, and a basic alt-azimuth GoTo mount.

https://stargazerslounge.com/forum/123-eeva-reports/

[Aetherum]

On 13/04/2021 at 00:28, Cosmic Geoff said:

Aetherum - check this section to see what I imaged with the same 102mm achro scope as yours, and a basic alt-azimuth GoTo mount.

https://stargazerslounge.com/forum/123-eeva-reports/

 

On 13/04/2021 at 00:28, Cosmic Geoff said:

Aetherum - check this section to see what I imaged with the same 102mm achro scope as yours, and a basic alt-azimuth GoTo mount.

https://stargazerslounge.com/forum/123-eeva-reports/

Geoff,

 

Thanks for the tip, before I can image some galaxies I have to find them first. I hope that will be possible under these polluted city skies. How does live stacking work exactly, does it accumulate the individual exposures?

 

Kind regards,

Robbe.

[Cosmic Geoff]

1 hour ago, Aetherum said:

Thanks for the tip, before I can image some galaxies I have to find them first. I hope that will be possible under these polluted city skies. How does live stacking work exactly, does it accumulate the individual exposures?

I don't know the technicalities but basically it adds the exposures and discards shots that cannot be synchronised (not enough stars, etc)  It will compensate for field rotation. 

I use Sharpcap and then increase the contrast in Adobe Photoshop Elements.

[malc-c]

Geoff,

The issue of field rotation tends to be less noticeable when wide field targets are selected and wide field lenses or scopes are used.  It's quite surprising just how fast we are rotating, and even in a 3 minute exposure stars will trail.  Because an ALT/AZ mount has to make up / down / left / right movements when tracking it can lead to poor quality results when used with higher magnifications or long focal length scopes.  Imaging is possible with an AZ mount, but there are restraints that make it just a little more challenging.

Software can help, and stacking images, either live or post session, and it's just a case of how well the software can deal with the rotation and overlap the points of light.

[happy-kat]

M42 with your mount and ST202, it's on this thread, an example.

https://stargazerslounge.com/topic/228101-the-no-eq-dso-challenge/?do=findComment&comment=3776550

As you are using a DSLR I would take lots of images and use deep sky stacker to stack them and then process the output in something like GIMP to start with.

 

 

Edited April 24, 2021 by happy-kat

[rotatux]

On 24/04/2021 at 13:55, malc-c said:

The issue of field rotation tends to be less noticeable when wide field targets are selected and wide field lenses or scopes are used

Again check the No-EQ challenge thread, you will find successful shots of both wide to narrow fields.

Field rotation is essentially the same whatever the scale, but its speed varies depending on sky location :

• Typically east and west, low to moderately high, are free from rotation, and that's where some people with good tracking mounts could achieve subs of 1 or 2 minutes (not my case  ); There's a PDF somewhere which gives max sub times per sky area for several latitudes. 20 to 45 seconds subs is most typical, but is enough for many deep sky objects.
• With wider fields you get more easily out of the rotation-free zones (so field rotation is actually *more* noticeable with wide fields in principle)

[Aetherum]

On 24/04/2021 at 11:04, Cosmic Geoff said:

I don't know the technicalities but basically it adds the exposures and discards shots that cannot be synchronised (not enough stars, etc)  It will compensate for field rotation. 

I use Sharpcap and then increase the contrast in Adobe Photoshop Elements.

Thank you for the tip. Unfortunately, I'm not running on Windows, so many applications I can't use. I only used GIMP so far and manual stacking wasn't a success. Great that it makes up for field rotation though..

[Aetherum]

On 24/04/2021 at 16:24, happy-kat said:

M42 with your mount and ST202, it's on this thread, an example.

https://stargazerslounge.com/topic/228101-the-no-eq-dso-challenge/?do=findComment&comment=3776550

As you are using a DSLR I would take lots of images and use deep sky stacker to stack them and then process the output in something like GIMP to start with.

 

 

I'll try M42, but I'll have to find stacking software that will run on macOS. Thank for the tip

[Aetherum]

On 24/04/2021 at 13:55, malc-c said:

Geoff,

The issue of field rotation tends to be less noticeable when wide field targets are selected and wide field lenses or scopes are used.  It's quite surprising just how fast we are rotating, and even in a 3 minute exposure stars will trail.  Because an ALT/AZ mount has to make up / down / left / right movements when tracking it can lead to poor quality results when used with higher magnifications or long focal length scopes.  Imaging is possible with an AZ mount, but there are restraints that make it just a little more challenging.

Software can help, and stacking images, either live or post session, and it's just a case of how well the software can deal with the rotation and overlap the points of light.

Thanks for the advice. Do you have any advice for software I can use on macOS?

[malc-c]

18 minutes ago, Aetherum said:

Thanks for the advice. Do you have any advice for software I can use on macOS?

Sorry... I don't use Apple products... a quick google and Starry Sky Stacker might be an option... Can't vouch for it as I've only ever used windows platform and applications

[happy-kat]

SIRIL stacks and runs on mac os

[Aetherum]

On 26/04/2021 at 16:46, happy-kat said:

SIRIL stacks and runs on mac os

I already got it, thanks! I'll try it out soon.