DSLR used for astrophotography???

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Re: DSLR used for astrophotography???

#101

Post by OzEclipse »


lsintampa wrote: Mon Jan 27, 2020 3:41 am
OzEclipse wrote: Mon Jan 27, 2020 3:16 am
lsintampa wrote: Mon Jan 27, 2020 2:01 am


So if I upgrade my CG-4 mount with the dual axis motors, can I mount the camera to the cg-4, say with a 200mm camera lens? I've read somewhere that the camera won't be aligned when mounted that way.

If you can find the reference, post it. It sounds wrong.

If the mount is polar aligned, anything driven while on the mount is also polar aligned. Perhaps the comment you read referred to GOTO alignment? I mount camera with 135, 200, 300mm telephoto lenses straight onto my Takahashi EM200, the mount is a clone of the Skywatcher EQ6. The principle is the same for a CG4. I do the polar alignment using APPS, Artificial Projected Pole Star alignment, then put a star dead centre of the field of the tele lens using full magnification live view and do a one star alignment in Sky Safari. From that point I have both GOTO and precise polar alignment.

Joe

https://www.cloudynights.com/topic/5030 ... -eq-mount/

This thread - see response 9
Hi,
There are many forms of 'alignment' in astronomy and AP.

That post #9 is referring to the misalignment of the auto-guider and the camera. This only applies of you are using some sort of auto-guiding. From what you have written, you want to add dual axis motors to your CG4 primarily to drive the polar axis then put a camera on the scope and do exposures tracked / driven by the motor but without an auto-guider system applying corrections.

Response 19 refers to GOTO alignment not polar alignment. If I have understood correctly, your CG4 is not a GOTO mount, so this problem also will not apply to you.

If that is the case, then as stated in my earlier post, "if the mount is polar aligned, anything driven while on the mount is also polar aligned."

Without guiding, you are relying on the precision of the drive system. Most drives have an oscillating error called periodic error. This is something like what your mount performance will look like.
periodic_error.jpg
Lucky imaging - you take a series of exposures, one after the other. Throw away the images where the error changes rapidly. The ticks and crosses indicate this. You do this by inspecting the images in the computer afterwards and throwing away those that show trailing, you don't need to produce an error graph.

cheers

Joe
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Re: DSLR used for astrophotography???

#102

Post by lsintampa »



Hi,
There are many forms of 'alignment' in astronomy and AP.

That post #9 is referring to the misalignment of the auto-guider and the camera. This only applies of you are using some sort of auto-guiding. From what you have written, you want to add dual axis motors to your CG4 primarily to drive the polar axis then put a camera on the scope and do exposures tracked / driven by the motor but without an auto-guider system applying corrections.

Response 19 refers to GOTO alignment not polar alignment. If I have understood correctly, your CG4 is not a GOTO mount, so this problem also will not apply to you.

If that is the case, then as stated in my earlier post, "if the mount is polar aligned, anything driven while on the mount is also polar aligned."

Without guiding, you are relying on the precision of the drive system. Most drives have an oscillating error called periodic error. This is something like what your mount performance will look like.

periodic_error.jpg

Lucky imaging - you take a series of exposures, one after the other. Throw away the images where the error changes rapidly. The ticks and crosses indicate this. You do this by inspecting the images in the computer afterwards and throwing away those that show trailing, you don't need to produce an error graph.

cheers

Joe

Joe, thanks for hanging in with me and all your feedback...appreciated.

To be clear I wanted to add the motors to my mount for tracking only so I may be able to take longer exposures using my DSLR. Meaning I would remove the OTA and mount the camera alone on the mount. I'd have to use some sort of dovetail to do that - I assume.

I understand now (thank you) it wouldn't matter where the camera is pointed (ie if I use a ball head). It would still "track" - assuming good polar alignment and albeit with periodic errors.

I'm not looking for magazine quality images, just family album quality. For now auto-guiding is not under consideration, but (I think) I'd like to at have that option available down the road. I want to make an educated decision on next steps.

Options (for me) as I see them now are:

1. The dual axis motors will not allow auto guiding - they would be tracking only. CONS - no upgrade ability for auto-guiding.
2. For about the same $$$ I found this item that claims to allow go-to and auto guiding to the CG-4 mount: https://astro-gadget.net/gadgets/telesc ... ledreameq3 CONS - not sure of the quality of the equipment - unknown vendor
3. This would allow go-to, tracking, and auto-guiding - and the head can be put on my CG-4 tripod with an adaptor: https://explorescientificusa.com/collec ... -iexos-100 CONS - Not sure if there are any?
4) Don't add motors to my CG-4 head, but use it's tripod to support a tracker like an iOptron or Sky-Watcher. CONS - most expensive option - although not a deal breaker - no goto, confusing to me as to payload capacities, optional equipment required, etc.

I'm leaning heavily towards the Explore Scientific PMC-Eight mounted to my CG-4 tripod.

Soon this thread will be put down to pasture - I promise.
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Re: DSLR used for astrophotography???

#103

Post by ARock »


lsintampa wrote: Mon Jan 27, 2020 4:28 pm
Options (for me) as I see them now are:

1. The dual axis motors will not allow auto guiding - they would be tracking only. CONS - no upgrade ability for auto-guiding.
2. For about the same $$$ I found this item that claims to allow go-to and auto guiding to the CG-4 mount: https://astro-gadget.net/gadgets/telesc ... ledreameq3 CONS - not sure of the quality of the equipment - unknown vendor
3. This would allow go-to, tracking, and auto-guiding - and the head can be put on my CG-4 tripod with an adaptor: https://explorescientificusa.com/collec ... -iexos-100 CONS - Not sure if there are any?
4) Don't add motors to my CG-4 head, but use it's tripod to support a tracker like an iOptron or Sky-Watcher. CONS - most expensive option - although not a deal breaker - no goto, confusing to me as to payload capacities, optional equipment required, etc.

I'm leaning heavily towards the Explore Scientific PMC-Eight mounted to my CG-4 tripod.

Soon this thread will be put down to pasture - I promise.
1. There are also some unconventional hacks to the cg-4 controller to enable ST-4 guiding. Look for the shoestring astronomy mod. Not very common though....
https://www.cloudynights.com/topic/3719 ... zed-mount/
An user's photos using it
https://www.cloudynights.com/topic/6021 ... ?p=8287669

3. The iExos-100 has been getting a lot reviews lately. The CONS are the lightweight tripod, no polar scope, no fine azimuth adjustment. For a DSLR and lens or a small telescope though, it might be enough, if you can do drift alignment. Azimuth adjustment can be added using a $90 kit with some drilling the tripod. If you can adapt it to your CG-4 tripod, it will improve some.

There is another DIY approach, is to add your own motors and controllers to the CG-4 using the ONSTEP framework. It needs some knowledge of electronics and computers, but there is big community behind it to help. Will allow you to add Pulse Guiding. Search for CG4 in
https://onstep.groups.io/g/main/wiki/Sh ... ith-OnStep

Note that with Star trackers and the iEXOS-100 you are reaching the $400 cost mark for really low end AP gear. The next level up are the $900-$1000 mounts which will save you a lot of grief.
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Re: DSLR used for astrophotography???

#104

Post by JayTee »


Please read this post, it may have some good ideas for you.
viewtopic.php?f=68&t=6661

Cheers,
JT
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Re: DSLR used for astrophotography???

#105

Post by OzEclipse »


lsintampa wrote: Mon Jan 27, 2020 4:28 pm

Hi,
There are many forms of 'alignment' in astronomy and AP.

That post #9 is referring to the misalignment of the auto-guider and the camera. This only applies of you are using some sort of auto-guiding. From what you have written, you want to add dual axis motors to your CG4 primarily to drive the polar axis then put a camera on the scope and do exposures tracked / driven by the motor but without an auto-guider system applying corrections.

Response 19 refers to GOTO alignment not polar alignment. If I have understood correctly, your CG4 is not a GOTO mount, so this problem also will not apply to you.

If that is the case, then as stated in my earlier post, "if the mount is polar aligned, anything driven while on the mount is also polar aligned."

Without guiding, you are relying on the precision of the drive system. Most drives have an oscillating error called periodic error. This is something like what your mount performance will look like.

periodic_error.jpg

Lucky imaging - you take a series of exposures, one after the other. Throw away the images where the error changes rapidly. The ticks and crosses indicate this. You do this by inspecting the images in the computer afterwards and throwing away those that show trailing, you don't need to produce an error graph.

cheers

Joe

Joe, thanks for hanging in with me and all your feedback...appreciated.

To be clear I wanted to add the motors to my mount for tracking only so I may be able to take longer exposures using my DSLR. Meaning I would remove the OTA and mount the camera alone on the mount. I'd have to use some sort of dovetail to do that - I assume.

I understand now (thank you) it wouldn't matter where the camera is pointed (ie if I use a ball head). It would still "track" - assuming good polar alignment and albeit with periodic errors.

I'm not looking for magazine quality images, just family album quality. For now auto-guiding is not under consideration, but (I think) I'd like to at have that option available down the road. I want to make an educated decision on next steps.

Options (for me) as I see them now are:

1. The dual axis motors will not allow auto guiding - they would be tracking only. CONS - no upgrade ability for auto-guiding.
2. For about the same $$$ I found this item that claims to allow go-to and auto guiding to the CG-4 mount: https://astro-gadget.net/gadgets/telesc ... ledreameq3 CONS - not sure of the quality of the equipment - unknown vendor
3. This would allow go-to, tracking, and auto-guiding - and the head can be put on my CG-4 tripod with an adaptor: https://explorescientificusa.com/collec ... -iexos-100 CONS - Not sure if there are any?
4) Don't add motors to my CG-4 head, but use it's tripod to support a tracker like an iOptron or Sky-Watcher. CONS - most expensive option - although not a deal breaker - no goto, confusing to me as to payload capacities, optional equipment required, etc.

I'm leaning heavily towards the Explore Scientific PMC-Eight mounted to my CG-4 tripod.

Soon this thread will be put down to pasture - I promise.
Almost all small cheap mounts will have larger periodic errors limiting the accuracy for photography. Be careful how much you invest in this venture. You spend a hundred here and a hundred there and pretty soon it adds up to a big slice of the price of a mount that is far more capable for AP. I have no experience with CG4 mounts can but some are reportedly quite good others mediocre.

1. As noted by AROCK, auto-guiding can be implemented. Before spending money on drives only, think ahead where this will take you.

2. Not familiar with this product so can't comment myself.
read this http://www.astronomyforum.net/telescope ... m-eq3.html
GOTO is only 60X siderial speed - very slow - 12 minutes to go to the opposite side of the sky.
Even my mount at 350X (2 mins) seems slow. Do you need this GOTO for wide field photography?

3. Not familiar with this product. You'll need to look for independent reviews

4. People have used these for short exposures <2min with up to 200mm lenses. The Skywatcher has ST4 auto-guider input but no facility for declination corrections so your polar alignment needs to be spot on.

Before spending a whole lot of money, I suggest you hone and practice your polar alignment skills. All of the solutions you are examining rely on very accurate polar alignment. The tech won't do that for you. You can do this without buying a drive. You don't even need to continually adjust. You will need some sort of crosshair. But you can scratch a couple of lines into a piece of clear photocopy film or perspex. cut it so that it just sits in an eyepiece at the field stop. Defocus a bright star and then you don't even need any illumination.

Good luck
JOe
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Amateur astronomer since 1978...................Web site : http://joe-cali.com/
Scopes: ATM 18" Dob, Vixen VC200L, ATM 6"f7, Stellarvue 102ED, Saxon ED80, WO M70 ED, Orion 102 Maksutov, ST80.
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Re: DSLR used for astrophotography???

#106

Post by lsintampa »


OK, time to put this to bed. Thanks to all for your help.

After taking in the feedback from you all, and doing other research, looking at videos, reading reviews, etc. What I've concluded is that "for me" I'm going to upgrade my existing Celestron CG-4 mount with their dual axis motor unit. I'm also adding their polar scope. Will be mounting my DSLR to a good ball head with a plate mount that I can use to either replace the telescope on the mount with, or piggy back it to the telescope.

IMHO, this is a worthwhile investment to take me one step closer without really making a "bad" choice. The upgraded mount will have some value add in the event I ever want to sell it.

Thanks again.
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Re: DSLR used for astrophotography???

#107

Post by UlteriorModem »


Have you given thought as to the cost of a new mount that has guiding built into it, vs purchasing the motors and all the hassle of installing it.
Tom

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Re: DSLR used for astrophotography???

#108

Post by lsintampa »


UlteriorModem wrote: Tue Jan 28, 2020 7:15 pm Have you given thought as to the cost of a new mount that has guiding built into it, vs purchasing the motors and all the hassle of installing it.
Yup.... Just for example, the iEXOS-100 (entry level) is $350.00 MOL - on sale. I've seen some videos of what it can do and I'm sure it would work, but I think in the end that I'd not be happy with it. It has mixed reviews - some users are not so happy, others are. I was wanting to go that direction, but got turned around after watching some videos of it in action. Trackers - iOptron, etc. are pushing 400-600 by the time you're done, and that assumes you have a good tripod to mount them on... another $200-300. If I were to go for a goto mount with tracking built in, I'd be near $900.00 or more - for anything worth considering. The other options IMHO, are simply entry level and may be less expensive, but that also spells - lower quality.

The motors for my mount ($118.00) will add tracking - and for me at this stage, I think is worth the investment. It will provide me with experience and it should allow me to take longer exposures. That aside, it's an improvement to the CG-4 and should add some resale value down the road.

Trying to sell a used entry level goto - well good luck with that. It's something I'd rather not have to deal with.

THEN (he said) there is a whole bunch of other skills, beyond those I still need to acquire to TAKE photos, and that is being able to PROCESS them. That's another story yet to be told.
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Re: DSLR used for astrophotography???

#109

Post by UlteriorModem »


Okay just wanted to make sure you had considered that. Remember in AP the mount is everything!
Tom

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Re: DSLR used for astrophotography???

#110

Post by lsintampa »


So, I've been busy. Still making mistakes, but I think I'm getting the hang of things. Mindful that my equipment is border line low quality.

I upgraded my camera from D50 to D5300.
Figured out how to use live view for focusing - with help (thank you).
Got remote control app for the camera - allows phone to live view, set settings, and take photos.
Added polar scope and dual axis motors to my CG-4 mount.
For grins I picked up a Meade 60AZ-T to play with ($25.00).

I put that together last evening. It was a full moon but the side of my house allowed me to setup in the shade (ha). Of course polaris was now blocked from view, but I aligned the mount best I could using a true north compass. Target was M42.

Mounted the Meade (cheap scope) to a ball head on my mount. Took only 20 - 2 second pictures. I know - don't blast me, still just learning. No darks, no bias, just lights.

Deep Sky Stacker - managed to stack 9 pictures. I processed the stacked photo with GIMP. I have a trial for PI, but my attempt to use it failed. I'll try again later.

For me, I think this was worth the effort. I made a lot of mistakes and took a lot of shortcuts - i know. Just trying to learn and put together a workflow - one mistake after the other.

So, with motors running, I thought I had set up my exposure for 20 seconds each shot with a 2 second delay between shots. Alas, I had that backwards - so even though I thought I was taking 20 second exposures, they were only 2 seconds. The delay fooled me. (another learning curve)

Here's the best I could do with the 9 stacked photos using GIMP. I'll try PI later today.

Questions:

The FL of the inexpensive Meade is 350mm - I didn't really notice much star trails. So was I lucky with manually pointing the mount north or was I within the margin of error for that FL?

I processed single frames - then 6 stacked - then 9 stacked. I noticed a great difference with the stacked - even without darks or bias shots, etc. So would more 2 second shots keep improving the image? Reason I ask, is I've seen many very nice details of M42 with long exposures. So stacking then increases the details (sort of like slowly eliminates grain)??

Anyway, it was a learning experience and did give me hope that I'm at least moving in the right direction. I should have never taken a picture of the moon!
orion_9_stacked.jpg
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Re: DSLR used for astrophotography???

#111

Post by UlteriorModem »


Not bad. Looks like you got some coma or tilt in there though.
Tom

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Re: DSLR used for astrophotography???

#112

Post by lsintampa »


UlteriorModem wrote: Sun Feb 09, 2020 5:48 pm Not bad. Looks like you got some coma or tilt in there though.
I can understand both. First, it was a very inexpensive telescope. $25.00 like new.

The optic mount on the scope's focus tube is plastic and it would be shocking to think the camera was very secure. Additionally, the lens on the Meade 60AZ-T isn't really meant for AP.

Thanks!
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Re: DSLR used for astrophotography???

#113

Post by metastable »


nice pic
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