6 replies to this topic

[Astrojensen]

After many attempts, the Deep Sky Camera app finally worked on my OnePlus Nord CE3 Lite smartphone. And then I was promptly hit with a month-long period with constantly overcast skies...

 

The curse finally lifted somewhat last night, and I was able to try it out for the first time. And it really does work! After using the ProCam X Lite app, where I had to start each exposure manually, which could get rather tedious if I wanted many frames, using Deep Sky Camera was sheer bliss. 

 

It is not without its disadvantages, though. It has a STUPID file numbering system, that doesn't give new frames a consecutive number, but a seemingly random one, which means that when I try to upload them via USB cable, it puts all the images in the folder in a completely random order. Everything from the whole evening is thrown together in a huge mess. ProCam X Lite always sorted them nicely. 

 

Also, Deep Sky Camera doesn't have a good image previewer. Inspecting the image for focus, framing, etc., is not super easy. And you can't quickly flip through the images to check for altitude drift. I have to exit DSC and open the images in the phone's photo album and inspect them there. Fortunately, DSC seems to remember all settings, so it doesn't lose focus, while doing so. 

 

I also found out that DSC would occasionally crash to "desktop" ("phonetop"?) when I was trying to inspect the photos and then take several attempts to restart. 

 

But overall, once I get a new routine, it will still dramatically reduce the workload at the telescope. I can now observe visually for longer periods uninterrupted, while the phone and telescope take images. Yesterday evening, I was having a blast observing Jupiter in excellent seeing through my 152mm ED at 179x, while my 63mm Zeiss on the 1b mount took images with the phone and DSC app. Conditions for photo were very mediocre, with lots of drifting clouds, some haze, as well as a fair bit of wind made things a challenge. I had to discard many frames due to clouds, but managed to get five, quite decent images: 

 

 

First was, of course, M42. What else can you choose as a test on a December evening? I had to throw away several frames, due to clouds, and this is just 8 x 30 seconds! I also had to pull pretty hard in the contrast throttle handle, because of the bright background caused by clouds. The core is burned out completely, but I think it gives the image a sort of "old-school" charm of its own. 

 

 

M42 complex and surroundings. December 20th, 2024. Zeiss C63/840 on Zeiss 1b mount, 40mm GSO projection eyepiece, 21x, 2° TFOV. 8 x 30 seconds at 6400 ISO. OnePlus Nord CE3 Lite, Deep Sky Camera app. Stacked in DSS, processed in Windows Pictures.

 

Another perennial winter favorite is of course NGC 2024, the Flame Nebula. The Horsehead is actually also in the photo, but I don't have enough frames to pull it out, without REALLY opening up on the processing throttle, and then the image becomes way too noisy and ugly. The little reflection nebula below Zeta Orionis is NGC 2023. 

 

NGC 2024, December 20th, 2024. Zeiss C63/840 on Zeiss 1b mount, 40mm GSO projection eyepiece, 21x, 2° TFOV. 10 x 30 seconds at 6400 ISO. OnePlus Nord CE3 Lite, Deep Sky Camera app. Stacked in DSS, processed in Windows Pictures.

 

And we can't ignore the Pleiades, of course. This is just three exposures of 30 seconds each. I had to throw two away, and more wasn't possible, due to clouds. Thus the image is fairly noisy, but it still came out pretty decent, considering the conditions. 

 

M45, December 20th, 2024. Zeiss C63/840, 40mm GSO projection eyepiece, 21x, 2° TFOV. 3 x 30 seconds at 6400 ISO. OnePlus Nord CE3 Lite, Deep Sky Camera app. Stacked in DSS, processed in Windows Pictures.

 

M1, the Crab, is another winter highlight. 

 

M1 Crab Nebula, December 20th, 2024. Zeiss C63/840 on Zeiss 1b mount, 40mm GSO projection eyepiece, 21x, 2° TFOV. 8 x 30 seconds at 6400 ISO. OnePlus Nord CE3 Lite, Deep Sky Camera app. Stacked in DSS, processed in Windows Pictures.

 

And finally M35 and NGC 2158. I was a little shocked to see how well resolved NGC 2158 was, considering the small aperture and short focal length (110mm), but the phone camera has minuscule pixels and the seeing was also great, resulting in very compact, well-focused stars. 

 

M35 and NGC 2158, December 20th, 2024. Zeiss C63/840 on Zeiss 1b mount, 40mm GSO projection eyepiece, 21x, 2° TFOV. 12 x 30 seconds at 6400 ISO. OnePlus Nord CE3 Lite, Deep Sky Camera app. Stacked in DSS, processed in Windows Pictures.

 

 

Clear skies!

Thomas, Denmark

[c2m2t]

Hi Thomas!

Those are fantastic!! My question for you is...how are you holding/positioning your phone to the eyepiece? I am guessing, given the duration for individual frames, you must have some kind of phone holder affixed to your eyepiece. I am sure there are plenty of folks wanting to replicate your results!! Well done!!

 

Cheers, Chris.

[Astrojensen]

Hi Thomas!

Those are fantastic!! My question for you is...how are you holding/positioning your phone to the eyepiece? I am guessing, given the duration for individual frames, you must have some kind of phone holder affixed to your eyepiece. I am sure there are plenty of folks wanting to replicate your results!! Well done!!

 

Cheers, Chris.

Thanks!

 

I'm using this phone adapter: https://www.amazon.c...B01N9PQZIB?th=1

 

It's directly attached to this eyepiece: https://www.teleskop...er-kameras-1428

 

The correct distance between camera and phone is VERY critical! It needs to be within a millimeter or so. I needed to do a lot of experimentation to find the correct distance. As a general rule of thumb, the field stop must be in sharp focus. 

 

If possible, when using a reflector (with central obstruction) the magnification should be chosen so that the exit pupil is not larger than the camera aperture. On a refractor, this doesn't matter. Higher magnification (and smaller exit pupils) will result in slower f/ratio. If the exit pupil and camera aperture match, the combined system works at the camera f/ratio. The above images are shot at f/1.7. 

 

As in any form of astrophotography, focus is highly critical. I aim at a bright star, zoom in as much as possible, and focus via the live view. This works well. If the temperature is dropping, I check the focus between series of frames. 

 

Having a good, stable mount is also a must, just like in all other forms of astrophotography. I use an old Zeiss 1b mount that has a superb, smooth RA drive with only 3"-5" periodic error in a ten minute worm rotation. This ensures a very low frame loss rate, but I have also had surprisingly good results with a low-end EQ-3 mount! I just had to be ready to throw away some more frames or accept a shorter exposure time and take more frames to compensate. It goes without saying that polar alignment needs to be fairly good, but with the short exposures, you don't have to be completely fanatical about it. My Zeiss mounts doesn't even have a polar scope, so I just use the setting circles to set the mount to aim at Polaris and use the finderscope.

 

 

Clear skies!

Thomas, Denmark

[c2m2t]

Hi Thomas!

I am sure your reply will be very helpful to many budding astro-photographers!! 

 

I have far too many other cameras to be attempt imaging with my phone. One thing nice about your images, it provides the circular fov that we all experience at the eyepiece. I'm thinking that you might want to try experimenting with the settings to see if you can replicate the actual view your eye(s) is seeing at the eyepiece. I don't know how easy it is to be moving the camera/phone in and out of position for you to evaluate the image captured and what your actual eye is seeing and maintain focus. That may be too much to ask. Matching scopes side by side would make it a whole lot easier. 

 

Cheers, Chris.

[Astrojensen]

 

One thing nice about your images, it provides the circular fov that we all experience at the eyepiece. I'm thinking that you might want to try experimenting with the settings to see if you can replicate the actual view your eye(s) is seeing at the eyepiece.

I have already experimented quite a bit with that. Single exposures seem best for that, and you need to experiment to find the right exposure for the object. It's a bit challenging, but can give quite satisfying results. It's not entirely accurate, since our eyes work differently than a camera, and the camera picks up stars a LOT more than the eye, so the images tend to show way more stars than can be seen visually. 

 

Here's M81 and M82 as an example: 

 

 

M81/M82, April 6th, 1:05 UT. 63/840mm Zeiss, 40mm GSO, 21x. 30 seconds at 6400 ISO. Image completely unedited. Equivalent focal length, 110mm f/1.7.

 

It's not entirely accurate, but it does give a fairly good idea of what to look for in a small telescope. If I stack multiple exposures, it starts to bring out far more detail than the eye can see. 

 

 

Clear skies!

Thomas, Denmark

[c2m2t]

Hi Thomas!

Curious about the information below the most recent image..."Equivalent focal length, 110mm f/1.7"...how are you arriving at these values?? There is so much about optics that I do not understand...I keep saying that I am just a dumb photographer!! 

 

Cheers, Chris

[Astrojensen]

Hi Thomas!

Curious about the information below the most recent image..."Equivalent focal length, 110mm f/1.7"...how are you arriving at these values?? There is so much about optics that I do not understand...I keep saying that I am just a dumb photographer!! 

 

Cheers, Chris

The equivalent focal length is calculated by multiplying the camera focal length (5.24mm in this case) with the telescope magnification (21x). That is the effective focal length the system is working at. 

 

 

Clear skies!

Thomas, Denmark