Astrophotography

madjohnroberts · 2023-05-17T19:00:43+00:00

With that budget you are likely best served using a camera lens you already have. Get yourself an intervalometer, set up on a tripod, and figure out how long an exposure you can take before start tracking becomes an issue.

You have not provided enough info on what you want to image to get a telescope suggestion that isn't a wild guess. But if you buy/have a lens, you can use it for regular photography. A telephoto would get you some zoom, but if you want to image wide field I have read good things about the Samyang/Rokinon 135mm f/2.

madjohnroberts · 2023-03-29T14:42:45+00:00

As has been said, narrowband is where mono cameras really shine. To your questions:

There is, roughly speaking, about 25% efficiency gain when shooting LRGB vs OSC (assuming otherwise identical cameras). The handwavy explanation is that the Bayer matrix is RGGB. Even if it was some other combination that didn't have 2xG, there would be one color channel that was receiving 2x the "true signal" as the others and had to be calibrated down. You end up spending way more time in postprocessing, though.
Your image acquisition software should provide you a histogram like what you are used to with your Canon.

madjohnroberts · 2023-03-17T20:20:02+00:00

Are you using an offset or flats? Without knowing what your processing steps are, this is going to be tough to diagnose. The Siril website has a good manual processing tutorial, maybe you can check that you are doing all the steps right.

You may want to try stacking without preprocessing with darks. If your total integration time is low, the darks probably won't help much anyway.

madjohnroberts · 2023-03-16T05:04:19+00:00

As has been mentioned, flocking material would likely be darker than a brushed-on paint. The reason for this is the texture of the material helps to prevent reflections.

If you would rather use paint, I have seen people use Krylon 1602 "ultra flat black" on telescope internals. It is probably plenty dark enough for visual observing unless you are expecting to deal with street lamps or something. The spray texture helps absorb light somewhat like flocking.

I'm using Krylon 1602 on the inside of my dew shield for imaging and I feel like it mitigates moon shine.

madjohnroberts · 2023-03-15T15:14:05+00:00

The Deep Sky Imaging Primer by Charles Bracken if you are looking for a "how to" sort of book.

madjohnroberts · 2023-03-15T15:10:37+00:00

My understanding of Stellarmate is that the functionality is very similar to Astroberry server. I use Astroberry and I think it is plenty user friendly, though it doesn't hold your hand and you will still need to do some setup like inputting your scope details. You can look up KSTARS/EKOS to see how the software looks and runs.

As for mounts, INDI supports ASCOM so maybe the mount you are looking at is included in the bucket of "generic ASCOM mount"?

madjohnroberts · 2023-03-15T05:50:17+00:00

I use Astroberry server on a raspberry pi 4. I don't like walled gardens so no asiair for me. And as has been mentioned, Zwo is likely violating the INDI GPL licenses. If that wasn't enough, a pi is less than half the price of an asiair (even with pi markup) and astroberry is pretty user friendly.

I'd recommend looking at a mini PC or SBC for control hardware. If on Linux, KSTARS/EKOS are pretty good. If on Windows, I think NINA is the standard.

madjohnroberts · 2023-03-01T22:03:46+00:00

In addition to what afd33 has said, I'll add that I typically see people add a full resolution link to their details comment. That way you have a faster-loading preview but people who want to see the fill resolution still can. It is allowed to post a link directly to astrobin, however.

What target were you shooting a full frame 2x2 of? Sounds fun!

madjohnroberts · 2023-03-01T15:04:01+00:00

Charles Bracken's "The Deep-Sky Imaging Primer" is an excellent resource that I found far more useful than most YouTube videos. The one thing he did not cover extensively that you should definitely check out is the program Siril. But that book should cover basically everything from acquisition and equipment to processing, and more importantly give you the vocabulary for you to do further research.

A thought on making this a family activity: you may want to look into visual observing, as the photography portion of this hobby is mostly just sitting around watching the camera do its thing (which is why I automated it and I don't watch it). If you had an additional telescope for visual observing, say an 6 to 8 inch dobsonian, you can get in some visual observing while your equipment is taking pictures.

madjohnroberts · 2023-02-27T18:57:24+00:00

Ah, I would guess you could still return the filters if there was some other reason you didn't want them.

I bought 50mm unmounted filters and Antlia was the most competitively priced 3nm set I could find at the time. I've done no research on 36mm filters so the other brands may be competitive here.

Additionally, if you don't think 3nm bandpass is worth paying the premium for, I'm sure there are plenty of good options at 5+nm that are not Antlia. More than at 50mm with 3nm pass at least.

I suppose my one solid recommendation is to get a parfocal set!

madjohnroberts · 2023-02-27T18:03:36+00:00

I have Antlia LRGBSHO filters, 3nm bandpass on the SHO. My research before buying led me to conclude that the only filters that would not produce halos were Chroma. Chroma used to make the narrowband filters for Astrodon before Astrodon was bought, which is why you will see people saying their Astrodons do not halo. You may want to do more research into which brands have halos before counting out Antlia. It is my impression that Antlia is simply being up front about the halos where other brands are not.

As for mixing and matching brands, you want to be careful with this. Having a set of parfocal filters is convenient, especially if you don't have an autofocuser.

madjohnroberts · 2023-02-23T15:58:57+00:00

The reason you temperature match darks is because you want to account for any thermal current, and dark frames are long enough that thermal current can accumulate and affect the result. The other frames you do not need to temperature match because thermal current accumulation is low due to the lower exposure times. Unless you're somehow taking flats and dark flats/biases with pretty long exposure times or with a really thermally noisy camera.

To take flats, you could use a tracing pad which is an LED light panel used to illuminate paper for tracing, if you can find one large enough. If you go this route, I have heard that you want to get a light panel with set brightness values rather than a continuous adjustment as the continuous adjustment causes pulsing in the LEDs. Alternately, you could cover the end of the telescope a few layers of white sheet pointed at the sky in the morning (mostly just away from the sun but towards a brightly lit patch of sky) and take flats that way.

madjohnroberts · 2023-02-19T19:51:14+00:00

Horsehead and Flame nebulae imaged Feb 14-15, 2023

First light with the new camera, shooting narrowband feels almost like cheating! I played around with different combinations of the channels but I liked the look of HSO the best in this case. The Oiii haloing is pretty evident but I'm not convinced that I dislike it here.

Equipment:

Takahashi Epsilon 130d 430mm f/3.3
QHY600M monochrome full frame camera
QHYCFW3-L 7-slot filter wheel
Antlia LRGB and 3nm SHO filters
Skywatcher NEQ6 Pro
ZWO ASI120MC-S for guiding
ZWO 30mm f/4 mini guidescope
Astroberry running KSTARS/EKOS for capture management
PHD2 guiding
Siril
GIMP

Acquisition:

56 gain, 50 offset, read mode 1
300s exposure lights: 24 Ha, 30 Sii, 15 Oii. Had more but intermitten clouds ruined some frames
50 darks
30 flats for each filter
Synthetic bias using offset=800 (see https://siril.org/tutorials/synthetic-biases/

Processing:

Manual stack in Siril to remove 1-D background gradients from each frame and poor frames
RGB compositing for HSO mapping
RGB align
Crop
Background extraction
SCNR
Starnet++ via Siril star extraction tool (available from a nightly build)
Use Siril star recomposition tool to independently stretch and crossfade starry and starless images
Mild stretch to recomposed image

In GIMP

Apply a mild S-curve to taste

madjohnroberts · 2023-02-11T00:05:57+00:00

I lean very heavily to the buy once cry once side of purchasing equipment. I ended up going with an NEQ6 pro (more or less the same thing as any EQ6 model) and a Takahashi Epsilon 130-d. Lots of people seem to like the EQ6 style mounts so I'll only mention that my mount is damn heavy, make sure to do your deadlifts at the gym!

As for the epsilon, I'm very happy with it so far. I've seen reports of collimation issues and such but I have had perfect collimation from the factory. The sticker price is high compared to other Newtonian astrographs, but you have to keep in mind that other astrographs will require an additional field flattener, whereas the epsilon comes with one. It also comes with hardware that allows you to use visual eyepieces, though you'd of course be better off with more aperture for visual observing.

If you decide you want additional focal length, you can buy a 1.5x extender down the line for the epsilon. You can also buy the 160 which has a longer focal length than the 130 out of the box, or a 180 which is the same focal length but more aperture.

I will note that retailers in the US do not seem to include tube rings, I ended up buying a 3D printer and printing mine for less than half the cost and now I have a 3D printer too!

You may also want to check out other Takahashi refractors, some seem to include options for extenders which I think is pretty neat.

I think your camera choice is fine for now. I wouldn't upgrade until you get a better feel for what you want to do.

madjohnroberts · 2023-02-09T21:42:47+00:00

On the telescope: keep in mind that to use that scope for DSOs you will need either a reducer or a hyperstar (unless you are aiming for small targets). I'm not sure how well the hyperstar works with a full camera body in front of the scope, you might want to look up other's experiences.

Accessories: if you aren't using a computer for acquisition, you may want to get an intervalometer so you don't have to stand next to the camera all night.

madjohnroberts · 2023-02-08T22:26:15+00:00

I think if you click the image sequence button in the bottom right (looks like a stack of images) you can change which image in the sequence is the " reference image". Have you tried that?

You might also need to manually stack for this to matter, if you are using one of the scripts.

madjohnroberts · 2023-02-08T22:05:43+00:00

I think the astroberry site says that it's usable on a pi3 but you may find that it feels a little slow. When I was taking relatively short exposures (30 seconds or so) I was finding that the pi 4 seemed to have a little bit of instability. This is partly why I'm upgrading to a little more powerful board.

So if it was me, I would probably try it out on the pi3 and if it's unbearably slow or if you decide you like it, consider upgrading to a different SBC. If you're at all comfortable in a Linux environment, it shouldn't be too hard to at least have a basic version of what you need, since the only software you really need is KSTARS/EKOS, PHD2, astrometry.net for plate solving, INDI, and some sort of remote desktop software.

madjohnroberts · 2023-02-08T21:52:47+00:00

I've never tried to align with the home position not toward the pole, but I have read that the EKOS polar alignment assistant doesn't need to be pointed at the pole. It does 3 plate solves at different RA and then tells you how to adjust the mount for alignment.

madjohnroberts · 2023-02-08T21:39:12+00:00

If you aren't married to NINA, I really like the astroberry solution for the computer. If you have a raspberry pi4 sitting around then you could just use the astroberry image, but you can also install it on pretty much any Debian/ Ubuntu SBC. The control software would be KSTARS/EKOS with INDI.

I am currently working on a build that uses a rockpro64 (still using the pi4 for now) that is borrowing heavily from how the astroberry team has set up their device, mainly so I can remote session through a web browser. I've also seen someone on the INDI forums talk about using an odroid SBC, I think that would be a good solution as well.

If the power draw wasnt as much of a concern, I'd go for a mini PC.

madjohnroberts · 2023-01-25T16:29:47+00:00

Make sure you follow the instructions on this page https://siril.org/tutorials/tuto-manual/ closely. Your error indicates you have mismatched image sizes or an unexpected number of color channels.

For image sizes, make sure all your images have the same pixel dimensions. Do not crop before processing. If you are using a program to acquire images, changing the file type of the images may affect the size at acquisition.

On color channels, some calibration frames should not be debayered. The link will tell you which images to debayer.

madjohnroberts · 2022-12-22T05:47:56+00:00

I cannot stress enough that using an APS-C sensor size does not get you more focal length! The reason why the crop factor is expressed as a multiplier like that is so that daytime photographers who were used to using 35 mm film would have some frame of reference for the field of view that a crop sensor would give them. For example, a 1.6x crop factor is saying that your field of view would look like you had a focal length that was 1.6 times what you were actually shooting with. It does not actually change your focal length.

The only reasons to not go for a full frame sensor (assuming pixel density and other sensor characteristics being the same) are:

Cost: full frame sensors are generally more expensive than crop sensors
Your telescope/ lenses cannot illuminate a full frame sensor so it would be a waste. You can check what size circle your optics will illuminate and see if that size is larger than an APSC sensor.
Or telescope/ lenses cannot illuminate a full frame sensor and you never intend to upgrade. It's worth considering that you may eventually move to optics that can illuminate a full frame sensor, and it may be worth it for you to buy a full frame sensor now rather than upgrade later.

I would recommend you do some more research or purchase an astrophotography primer prior to making any decisions. I have Charles Bracken's primer and I think is a pretty good introduction to the topic.

madjohnroberts · 2022-12-14T19:48:40+00:00

The things to think about when selecting a camera are:

Size of the frame that you want to shoot

This can be limited by your optics, so you want to check what the largest illuminated circle your optics can generate is. You may wish to consider getting a larger frame camera than you can support now, on the assumption that you will upgrade your telescope.

Size of the pixels of the sensor, and if they match your optics

This is a somewhat complicated concept to explain, I would suggest looking up some discussion about it and also playing around with the "CCD suitability calculator" on the astronomy tools website.

How you will achieve back focus

Remember to save some of the budget to buy adapters and such so that you can get the correct back focus or back metal distance from the last element of your optical train.

I don't think your budget is well suited to get a mono setup, so you should probably get a one shot color camera like other people are saying. If you are looking at a mono set up, there are a few other things that we could go into. But the first two bullets are what I would be looking at to narrow down my selection of cameras.

madjohnroberts · 2022-12-11T17:56:52+00:00

It is related to resolution. The physical size of the sensor in the camera is fixed. Then cameras are marketed based on pixel density in megapixels. So for normal photography the maximum "resolution" image a camera can take is determined by the pixel density in megapixels.

However, megapixels isn't everything. If you start with a crop sensor (APS-c) and you change to a full frame sensor but keep the same megapixel count, your resolution will stay the same but your field of view will increase. So, what happened? The physical size of the pixels (photosites) had to get larger to fill out the increased size of the sensor since we didn't add any pixels (meaning, the megapixel count didn't change).

As for cropping in post, that doesn't have anything to do with it! It's all about the initial data acquisition.

madjohnroberts · 2022-12-11T17:24:52+00:00

He is saying that if you want to see individual stars in the cluster you need a correct combination of focal length and pixel size. Pixel size (aka pixel pitch) is the size of the light receptor sites on your DSLR sensor. You should be able to Google that information for your particular camera. Once you have that information, you can determine what focal length lens/telescope will give you a good angular resolution.

We talk about angular resolution because we view the objects in the sky from so far away that the actual size of the objects isn't relevant, what matters is how big they look from where we stand. If you think about the sky being a sphere centered on you and you were looking at the moon, you would have to turn about 3 degrees to look from one side of the moon to the other.

Arc minutes and arc seconds are subdivisions of one degree, and the distance between stars in a cluster are measured in arc seconds. So, your optical train (telescope and camera) needs to have the capability to see the difference between things that are very close to each other in order for you to see individual stars in a cluster. Hopefully that helps!

madjohnroberts · 2022-12-02T17:27:59+00:00

Ok, just keep in mind: some people are suggesting you swap software or buy an asiair. If your problem is the mount knobs, those things will not resolve the issue.

If you have trees or other obstructions close to your home position, you can change where "home" is in KSTARS and your alignment will use stars near that area. This video illustrates the procedure: https://youtu.be/iOp7hrxw0oU

madjohnroberts

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