Category Archives: Astrophotography

T-Mount Try Out

The T-Mount system was devised by Tamron in the 1950s to allow their lenses to be used on many different cameras. It’s also the system used to attach a camera to the prime focus of a telescope. I’d never tried it, so I ordered a T-Ring and Sony adapter and gave it a go.

All of these images were made with a Sony A6600 APSC camera mounted on a NexStar 6SE telescope at prime focus using the T-Mount adapter. I captured multiple frames for each and processed them with astro photo capabilities added recently to Affinity Photo.

In prime focus astrophotography, you’re using the telescope as a lens, mounted directly to your camera. There’s no eyepiece involved, although you can insert additional optics into the light path. I used three different configurations.

1. Prime focus, with a Celestron f/6.3 Reducer Corrector. Equivalent focal length = 1.5 x 1500 x 0.63 = 1418mm

In the first image I used a Reducer / Corrector. This both widens the field of view / lowers the focal length, and flattens the field to enhance sharpness at the edges. This worked OK, but did have some obvious vignetting that was hard to deal with in post processing.

Luna 2.Prime focus. Equivalent focal length = 1.5 x 1500 = 2259mm.

Image 2 is the same setup, but straight from the telescope to the camera. There was no vignetting and I think the image quality is very high. The featured image at the top of this post is a crop from this photo. (Note: This one is posted on Flickr and is worth a click to see in greater detail. Click it twice when you get there to enlarge it.)

3. Prime focus with a Meade 2x Barlow lens. Equivalent focal length = 1.5 x 1500 x 2 = 4500mm

And finally, image 3 uses a Barlow lens, which is like a 2x extender. The image quality in this one is not as good. That could be due to degradation from the Barlow, a slight mis-focus, or vibrations / motion (or all three!).


  • Check and double check all settings and adjustments.
  • These are longer focal lengths than anything I’ve ever tried before. Technique is super important and it’s hard to know if you’ve messed up until you get things on the computer later.
  • The straight prime focus method works very well. The image quality is the best I’ve gotten through the telescope, It’s better than the afocal approach (camera lens through an eyepiece) I used for this post.
  • The reducer / corrector works OK, but I’ll probably shy away from it unless I need a wider field of view. And if that’s the case I think I’d try using piggy-back photography first.
  • The 2x Barlow approach is challenging. The magnification makes any focus or motion issues much worse. This should probably be reserved for planets, and used as a second option to straight prime focus or piggy-back with a long telephoto lens.
  • There is a lot to learn about astro photography!

Thanks for stopping by and reading my blog. Take care of yourselves and each other. And if you can – make some (astro) photos!

©2021, Ed Rosack. All rights reserved

The Telescope

Comet Neowise and the Great Conjuction in 2020 made me think about the telescope I’ve had in the closet for many years. I’m happy with the images I made of those two events, but I regret not trying to use the scope to photograph them.

I’d only ever used it for observing. Photographing through a telescope requires a much higher level of knowledge and technical skill. In addition to knowing how to set up and align the scope and camera, you have to understand and balance many more factors: camera (ISO, aperture, exposure time, focus, …), astro (atmosphere, alignment / tracking, field rotation, …) and post processing. So I thought I’d try a couple of shots to see what it could do.

Earth’s natural satellite. Using a Sony DSC-RX100M3 camera (1″ sensor), afocal through Celestron NexStar6 SE scope and 40mm eyepiece; Thirteen frames, manually aligned in photoshop and blended with smart stack mode median.

I used the moon to get everything set up and tested. Next I wanted to try to photograph a Deep sky object. They’re plentiful, but harder to find or even see. I picked the Orion Nebula as my second target – it’s probably the easiest DSO. Even here in my back yard, Orion’s belt stands out.

Orion Nebula
Orion Nebula. Same setup as above, using six frames instead of thirteen.

I know these aren’t Hubble level images or even very good amateur astronomer images. But I’m pleased with how they turned out. I want to continue exploring photography with the telescope and see how well it can work in my urban (and light polluted) environment. If I make some progress, I’ll share the images with you.

Thanks for stopping by and reading my blog. Take care of yourselves and each other. And if you can – make some (astro) photos!

©2021, Ed Rosack. All rights reserved

Are you ready for the Great Conjunction?

I’m posting early this week to give you a little advanced notice on an upcoming astronomical event.

A Great Conjunction is when the planets Jupiter and Saturn appear closest together in the night sky. The one happening next Monday (21 December) is the closest they’ve been since 1623. Here’s a Wikipedia article with more info:

Kevin M ( motivated me to go out and practice for it this evening. My first attempt is below.

Io, Jupiter, Europa, Ganymede, Callisto, Titan, and Saturn (bottom to top)Io, Jupiter, Europa, Ganymede, Callisto, Titan, and Saturn (bottom to top)

These planets are much brighter than their moons, so to get an image with a little detail in the planets and still show the moons requires stacking multiple frames. This one is a total of 5 frames – 4 for the planets (exposed at ISO 800, f/9, 1/250); and 1 frame for the moons (ISO 800, f/9, 1/40). It’s been heavily cropped and then digitally zoomed with ML Super Res in Pixelmator Pro.

Here’s a diagram from the SkySafari program identifying the objects and their positions for tonight.

 And this is the diagram updated for Monday night:

These are at the same scale, so you can see how much closer they’ll be on the 21st.

I’m hoping the weather will be clear. If so, I plan to at least make another image using tonight’s approach. But I’m also thinking about digging out my telescope. I haven’t used it in a long time. If I can get it running and aligned I should be able to make a little better photo. I guess I’ll see…

Are you going to try and photograph this? If so, I’d really like to see your images.

Thanks for stopping by and reading my blog.Take care of yourselves and each other. And if you can – capture a conjunction!

©2020, Ed Rosack. All rights reserved

12/22/20 edit:

Clouds last night were challenging.  This was the scene at sunset:

And this is how it looked once it was dark enough to see the conjunction:

I went ahead and made some frames and this is the best of the bunch (same approach as above except I didn’t use ML Super Res in Pixelmator Pro this time).  Click on this one to view a larger version on Flickr.

Great Conjuction, 12-21-2020Great Conjuction, 12-21-2020. Left to right: Callisto, Io, Ganymede, Jupiter, Europa, Saturn

I did get the telescope out and tested. It seems to work fine but given the seeing conditions, I didn’t take time to set up and use it. I think I’ll save that for a future project when those two planets are higher in the sky (although not in conjunction!).

Comet Stacking

I’ve seen some awesome images of Comet Neowise C/2020 F3. I’m sure you have too. Did you make any photos of it? Then you might have a better image than you think, just waiting to be processed. Let me explain.

Neowise.Central Winds Park. 7/16/20. Single exposure at 85mm, f/2.8, 8s, ISO 400

Lynn and I went up to Central Winds Park in Winter Springs to see if we could spot Neowise. This park is on the south shore of Lake Jesup and has less light pollution to the north than we do in our neighborhood. Once it was dark enough, we could easily find it in binoculars, but it was very hard to pick up with just our eyes.

I went back a few days later with my long lens to try for a close up.

Comet Neowise C/2020 F3

Neowise. Central Winds Park. 7/19/20. 3 exposure stack, 600mm, f/6.3, 2s, ISO 3200 – 6400

I made a lot of frames of the comet on that trip, trying to find optimal settings for a single exposure. Almost all of the really spectacular images that you’ve seen are probably from a tracking mount, with multiple frames that are aligned, stacked, and processed together to reduce noise and bring out faint detail. I wasn’t trying to do any of that.

But after several attempts to get the best image I could out of what I’d captured, I realized I might have multiple frames I could stack too. So going back through my RAW captures I found three photos to try. They weren’t ideal since they were at different ISOs but I thought it was worth a shot. Here’s a before / after of a single RAW image compared to a stacked composite from three frames.

Comparison of a single RAW frame to the stacked, 3 frame final image

If you’re an astrophotographer, you already know all this. And you probably have some task specific software to align / stack / process images. If you’re not an astronomy buff, then do a web search for “photoshop manual align astro layers” and you’ll find a lot of info on how to do this without any extra programs – which is how I processed mine.

This is only the 3rd or 4th comet I’ve seen and the very first that I’ve tried to photograph. The first one I saw was Halley’s Comet back in 1986. I remember how exciting it was to show it to Lynn and Mike. I had a camera (and a telescope) then, but photos like these with that equipment would have been next to impossible. Photography has come such a long way!

So, if you made any Neowise photos, sort through them for frames you can try to stack. You may be surprised at the improvement you can get.

Thanks for stopping by and reading my blog. Hang in there and take care of each other. And if you can – stack some photos!

©2020, Ed Rosack. All rights reserved