12 replies to this topic

[DavM]

Hello all, I've been doing deep sky imaging for about 5 years and intend trying solar imaging during the summer months. I will be using the Daystar Quark Chromosphere

 

I have an ASI 071 MC Pro, an ASI 120MC  and an ASI 120mm mini.

 

Further, TS 80mm f6 APO triplet refractor (480mm) and TS 0.79 reducer/flattener, which makes it an ~f4.7 at 388mm focal length.

 

My questions:

 

which camera would be best for this endeavour?

 

and can I still use the reducer in front of the diagonal, together with a IR/UV block filter screwed into the reducer?

 

Thanks in advance

Regards

Dave

[Tapio]

Mono camera is better but ASI120 has quite small sensor.

But if you use the reducer you can just (only just) fit sun in image.

You can test it here:

https://www.12dstrin....uk/fovcalc.php

 

Results
FOV: 42.97' x 32.23'
Resolution: 2.01"/pixe

[DavM]

Hello Tapio, many thanks for your speedy reply, and thanks for the link to test. I think the ASI 071 MC Pro will work nicely, possibly making a mosaic for a full disk! The 120mm will maybe work for closeups.

 

Regards 

 

Dave

[cmas]

I have to same OTA. I used it with the following imaging train as the Quark has a built-in 4.2x:

 

A) 90 mm diameter D-ERF from Baader

B) TS 80/480 triplet

1) Baader variable length T2-T2 extension

2) T2-2" adapter

3) Chromo Quark

4) Quark to 2"

5) Daystar 0.5x flattener (basically any decent one will do)

6) 20 mm extension tube

7) ASI178mm camera

 

https://www.flickr.c...08/50880999367/

https://www.flickr.c...08/50881004452/

 

The "thing" in business end of the OTA in the above image is just a DIY protective sleeve around the DIY D-ERF housing. I didn't have an image showing the D-ERF directly. And the cable is for a DIY focus motor.

 

So no diagonal. I would not use any diagonal unless you have to have for some reason (quickly changing to visual is the only reason I can think of). With that OTA you can build your setup like mine if you like, no need for diagonal. I choose to use full aperture D-ERF in front of the OTA - it'll give you best results most likely (lowest amount of excess heat into the OTA). If you use D-ERF in front of the OTA, you will not need any UV/IR blocking filter.

 

ASI178mm has a sensor with about 9 mm diagonal. Your ASI071MC pro has a sensor with a diagonal of about 28 mm. ASI120 has sensor diagonal of about 6 mm. Chromo Quark blocking filter is 12 mm and free etalon aperture is 20 mm according to the manual, see e.g. http://www.sunfield....QuarkManual.pdf so big sensors cannot be used without ROI / cropping.

 

With my setup I used to bin 2x2 or 3x3 my ASI178mm due to seeing conditions for best results. Thus, you need to test, but I would start with 120MC. 

 

Remember to take flats (flat video). You will need them. It's easy via unfocusing the image a bit if the whole sun is not visible at once.

 

If you end up with Newton rings, you may need to tilt your camera in respect to the optical axis. If there is only a small amount of Newton rings visible, flats with take care of that (this was the case for me). 

 

For solar push your FPS as high as you get. It's not called lucky imaging for nothing

 

My setup was able to produce images like this when everything was optimized and weather allowing:

https://www.flickr.c...08/34979375354/

 

All in all, it's a nice scope for solar work with Chromo Quark. I'll bet that you'll get nice images with 120MC, later if you like to continue you could consider a black and white relatively small sensor camera to optimize your setup.

Edited by cmas, 27 January 2021 - 07:31 AM.

[hopskipson]

Hi Dave

 

The Quark, with its 4.2x telecentric, needs an F/28-40 to give the best contrast leading to more details on surface features.  Therefore any focal reducer needs to be after the Quark.  Most users have a 174MM and a 0.5x reducer in front of the camera to best sample the Halpha wavelength.  I'm not familiar with the cameras you mention but they need to have relatively large pixels or possibly use of a 0.3 reducer to make them ideal.

[DavM]

Hi cmas, many thanks for your extensive reply. This gives me plenty of food for thought untill the Daystar arrives!

I have plenty of extension tubes but the added expense of an ERF at the front of the scope was not what I was contemplating.

I will certainly try without the diagonal and try and fit the 2" IR/UV filter somewhere in the train.

 

Thanks again

 

Regards Dave

[DavM]

Hi James, thanks for your reply and that's what I was afraid of, the reducer has to be after the Quark!

I will be trying solar imaging with the camera's and scope I already have for Deep Sky imaging.

The asi 071 mc pro has 4.78 pixels! The two 120 camera's have 3.75 pixels.

 

Regards

Dave

[MalVeauX]

Hello all, I've been doing deep sky imaging for about 5 years and intend trying solar imaging during the summer months. I will be using the Daystar Quark Chromosphere

 

I have an ASI 071 MC Pro, an ASI 120MC  and an ASI 120mm mini.

 

Further, TS 80mm f6 APO triplet refractor (480mm) and TS 0.79 reducer/flattener, which makes it an ~f4.7 at 388mm focal length.

 

My questions:

 

which camera would be best for this endeavour?

 

and can I still use the reducer in front of the diagonal, together with a IR/UV block filter screwed into the reducer?

 

Thanks in advance

Regards

Dave

Hi Dave,

 

Don't use a reducer before the Quark, keep your native focal-ratio before the Quark as long as possible. The mica-spaced etalon's performance is based on a more narrow light cone and parrallel rays (this is why the telecentric amplifier is in there at 4.3x power). After the etalon and blocking filter, you can reduce or do anything you wish after that point without harming the performance of your etalon, and anything you do after the etalon should be to support getting an ideal sampling match between your pixel size and the focal-ratio of the wavelength in use (656nm). So use your 80mm F6 natively; if you want to improve contrast, mask the aperture to 65~70mm to get a longer focal-ratio to get to F30+ on  your Quark's etalon. Or just for now use it at F6 natively and see what you see to get an idea of things before diving deeper for the moment. Don't use a digonal unless you have to, it adds nothing but another dusty surface and it puts the Quark in direct sunlight exposure (mask your Quark from direct sunlight to avoid overheating otherwise). The UV/IR block filter should be inserted onto something that inserts into your focuser, as deep into it as possible into the unfocused beam. Ideally this would be on a threaded 2" extension nose as you'll need them anyways when you remove the diagonal to get the focus distnace spacing back for the Quark; if you use the diagonal it will thread onto the nose of the diagonal that inserts into the focuser.

 

If you use your 80mm F6 natively with the Quark, the result is F25.8 and if you follow that with a 0.5x focal reducer to get F13 you can sample with 3.5um pixels essentially, or close. So then your 120 sensors with 3.75um pixels would be the best match. But those sensors are also super small so your FOV will be quite narrow. Don't bother using the "mini" version with USB2, it will be too slow of FPS to bother attempting lucky imaging. If you use the larger pixels of your 071 sensor, you'll be under-sampling if you focal-reduce by a lot, or over-sampling if you do not focal reduce by a little. The FOV of your 071 is larger of course, but at 10 FPS you won't get much data through bad seeing, making it even less useful. So you'll likely want to ROI (crop) the FOV to increase FPS, aim for something closer to 30FPS, whatever reduction it takes to get there, if you want to lucky image through bad seeing. Otherwise, get a more appropriate fast FPS camera for solar imaging with pixels in the 3.X range for your setup. I wouldn't fuss too much about it, just get it going and get some experience first. A lot of this won't matter if your seeing is really bad anyways.

 

Seeing is everything. You're always at the limit of your seeing conditions. Get some time and experience imaging with what you already have first. Then, if you're really into it and you want to take the next step and your seeing conditions can support it, I would suggest rebuilding a more ideal setup to use your Quark with (ie, a much longer focal-ratio scope and a different camera entirely).

 

Very best,

[DavM]

Many thanks for your wise words and construcive advice Marty, I've been following your comments here on CN and appreciate your answering my questions.

Just like deep sky imaging, it's all about using what you have and getting experience.

 

Regards

 

Dave

[spacetourist]

Seen some good h-alpha images with the "new" asi 462mc camera. They say, in acts as monochrome in infrared.

[MalVeauX]

Many thanks for your wise words and construcive advice Marty, I've been following your comments here on CN and appreciate your answering my questions.

Just like deep sky imaging, it's all about using what you have and getting experience.

 

Regards

 

Dave

Hi Dave,

 

I'm attaching a simple spread sheet calculator series that I've written and simplified. It can be used to figure out angular resolution for seeing conditions, per wavelength, apertures associated with them per wavelength, focal-ratios for critical sampling for a given seeing and/or for ideals. You simply input your aperture, seeing (if known), pixel pitch of a particular camera, etc. Some notes and instructions included. But you can play around with it to get an idea of what kind of seeing you need to max out a particular imaging train at a given wavelength with a given aperture and pixel size. And you can use it to simply know what you could potentially use to maximize your actual current seeing conditions in a particular wavelength. Knowing these values helps you select things like cameras to best sample for a wavelength at a focal-ratio under identified seeing conditions.

 

An example use:

 

Quark with 4.3x telecentric HA filter

Seeing conditions: averaging 2 arc-seconds

Ideal aperture for 2 arc-second seeing in terms of angular resolution of 656nm (HA) is approximately 80mm

80mm F7.5 is a common refractor, so let's use that

Quark + above scope results in F32.35 focal-ratio; to bring this down to something useful, let's use a 0.5x focal reducer, to F16.

4.2um pixels will critically sample 656nm wavelength at approximately F16 (so target pixels around that size, or slightly larger, to sample or under-sample assuming the given seeing conditions).

When selecting something, select towards whatever results in slight under-sampling, rather than over-sampling with the assumption that seeing will generally always be worse than perfect.

 

Very best,

Attached Files

•  Angular Resolution, Seeing & Critical Sampling Calculator (Martin Wise, 01272021).xls   12KB   18 downloads

Edited by MalVeauX, 27 January 2021 - 08:51 PM.

[DavM]

Hi Marty, fantastic! Thanks for taking the time to put this together, much appreciated 

 

Dave

[Lost in Space]

Hi Dave,

 

I'm attaching a simple spread sheet calculator series that I've written and simplified. It can be used to figure out angular resolution for seeing conditions, per wavelength, apertures associated with them per wavelength, focal-ratios for critical sampling for a given seeing and/or for ideals. You simply input your aperture, seeing (if known), pixel pitch of a particular camera, etc. Some notes and instructions included. But you can play around with it to get an idea of what kind of seeing you need to max out a particular imaging train at a given wavelength with a given aperture and pixel size. And you can use it to simply know what you could potentially use to maximize your actual current seeing conditions in a particular wavelength. Knowing these values helps you select things like cameras to best sample for a wavelength at a focal-ratio under identified seeing conditions.

 

An example use:

 

Quark with 4.3x telecentric HA filter

Seeing conditions: averaging 2 arc-seconds

Ideal aperture for 2 arc-second seeing in terms of angular resolution of 656nm (HA) is approximately 80mm

80mm F7.5 is a common refractor, so let's use that

Quark + above scope results in F32.35 focal-ratio; to bring this down to something useful, let's use a 0.5x focal reducer, to F16.

4.2um pixels will critically sample 656nm wavelength at approximately F16 (so target pixels around that size, or slightly larger, to sample or under-sample assuming the given seeing conditions).

When selecting something, select towards whatever results in slight under-sampling, rather than over-sampling with the assumption that seeing will generally always be worse than perfect.

 

Very best,

This is awesome, Marty!!!  You are a valued and treasured resource!!!