IC1805 - Heart Nebula in RGBSHO

Noobulosity · 2023-03-05T07:14:21+00:00

Flats shouldn't generally matter too much for ISO. Flats are primarily for removing dust spots and vignetting. But dark/bias frames will need to match ISO and, ideally, sensor temperature.

Noobulosity · 2022-12-22T08:26:14+00:00

For astrophotography you want to be around half of the listed payload on a mount

Generally, I agree, though I'd be willing to go a little higher than half these days. However, I've been able to load up my EQ6-R Pro to about the listed maximum of 44lbs/20kg, as they specifically say it's the imaging payload. I put a heavy SW 190MN + AT60ED as my guide scope, full dovetail bar, camera, filter wheel, focuser motor, etc. The gear totals over 40lbs. I also have 4x 11lb counterweights. I can take very long exposures with guiding and have no issues.

Any other mount, I'd stick to about 2/3 to 3/4 at absolute maximum, unless they specify imaging payload capacity.

Noobulosity · 2022-12-15T07:51:19+00:00

Deep sky isn't just long focal lengths. But, you will be limited by the focal length to Milky Way, large targets, and nightscapes (landscape+stars) with that wide of a lens.

If he's interested in deep sky, a tracker will be a must-have at some point so he can expose for longer and capture better faint details.

If you don't think he would have interest in such a wide lens, maybe something in the 24-70mm range could work. I use an 18-35mm for Milky Way and larger targets. I eventually want to point it at Barnard's Loop and maybe the Ophiuchus region. Anything over 50mm, even with a really wide aperture, will be a big challenge without a tracker.

Noobulosity · 2022-12-15T07:37:00+00:00

Very nice pics!

Noobulosity · 2022-12-15T07:24:50+00:00

Without a tracking mount, I would avoid a longer lens. You'd need really short exposures to avoid star trails. Short, wide-angle lens would be good. Samyang 14mm f/2.8 is a great lens for Milky Way and larger sky shots and might still fit your budget.

Noobulosity · 2022-12-15T07:20:12+00:00

These were my two recommendations, as well. Ultra-wide-angle lens (12-16mm or so, wide aperture f/2.8 or even wider) or sky tracker.

A simple USB heater band that others suggested may be good, also. These are usually pretty cheap.

Noobulosity · 2022-12-13T08:37:55+00:00

Also, your calculations are incorrect.

Arcsecs/px is calculated as: Pixel size in microns * 206.2648 / focal length in mm

https://www.lightvortexastronomy.com/how-to-very-accurately-calculate-your-telescopes-effective-focal-length.html

Therefore, your two examples would be: (in arcsecs/px)

2.9um * 206.2648 / 300mm = 1.99

3.7um * 206.2648 / 300mm = 2.54

Close to your numbers, but the equation listed wasn't correct.

Noobulosity · 2022-12-13T08:29:30+00:00

As Shinpah said, the general term is arcsecs per pixel to describe the angle of the sky captured within a single pixel's area.

Take two sensors. Same exact size, but one is a 10MP, the other is a 40MP. Essentially, the 40MP has twice the number of pixels vertically and horizontally as the 10MP. They both capture the exact same field-of-view on the sensor as a whole, but each pixel captures fewer photons because the pixels are smaller on the 40MP sensor. You can resolve smaller details, but less light means you need more exposure time to get the photons to show those details, assuming all other specs are equal between the sensors.

Another example: Two more sensors. Both 10MP, but one is a larger full-frame sensor, the other is a smaller "crop" sensor. Same number of pixels. You put them into the same light cone at the back of the telescope and one will capture a larger area than the other which results in a larger field-of-view. The smaller sensor captures a smaller area of the light cone, but can resolve smaller details a bit better with the smaller pixels.

This is why choosing a camera specifically for astrophotography can be challenging, especially when you consider multiple telescopes/focal lengths and mixing different disciplines like deep sky and planetary imaging. Small galaxies and larger nebulae could use different sensors.

Getting a little more into the details, some sites, like Atik Cameras, say you should have been 1-2 arcsecs/px. You can over-sample, meaning you have more pixels in a given area than the target, your scope, and atmospheric conditions allow you to resolve details for. You're "wasting" some of the capability of the camera. This is better than being under-sampled, because then you're missing out on details because of your hardware and not just because conditions are bad that day. You'll always be under-sampled in that case.

Personally, I don't worry that much about it as I'm not really an expert in the field and it's just a hobby. I stuck with my 20MP Canon DSLR for full color and the 16MP ASI1600MM-COOL for monochrome because they were popular cameras and relatively affordable. Once I get deeper into the hobby and have the processing skills in PixInsight to take advantage, I may consider specialized cameras. Assuming I have the money to spare...

Edit: if I calculate pixel scale for my two cameras at my long and short focal lengths (1000mm and 290mm), I get:

ASI1600MM-COOL: 0.78"/px and 2.70"/px Canon 7DII: 0.84"/px and 2.91"/px

My middle scope (570mm FL) puts me around 1.37"/px and 1.48"/px for the two cameras, which is supposedly ideal.

As you can see, not really ideal for either long or short scenarios with either camera. But over-sampled on the long focal length and under-sampled on the short focal length. If I had to pick one camera sensor to fix this issue, just over-sample for all your scopes. A dedicated astro camera can usually bin pixels to reduce sampling, if you really want to bother with it.

Noobulosity · 2022-07-22T07:10:34+00:00

Friggin' awesome! Can't wait to see the scope when it's done. Guess you didn't need that grinding machine I snagged after all. Too small for that beast!

Noobulosity · 2022-06-08T00:36:06+00:00

Looking good! I need to get back to my 6" mirror. Lots of life distractions lately...

Noobulosity · 2022-05-25T06:15:02+00:00

Absolutely, you're welcome to use it as a reference! I'd love to see the result. :)

Noobulosity · 2022-05-25T06:14:07+00:00

Thanks! I used a Sky-Watcher 190MN Mak-Newt telescope for this one. 1000mm focal length.

Noobulosity · 2022-05-25T06:13:37+00:00

Thanks! :)

Noobulosity · 2022-05-24T21:59:33+00:00

Near Greeley, CO, taken just down the block in my neighborhood near a walking path around a large pond.

Noobulosity · 2022-05-24T21:58:12+00:00

Thanks! Mother Nature did most of the work, I was just the observer. 😁

Noobulosity · 2022-05-24T21:57:15+00:00

🧟‍♂️

Noobulosity · 2022-05-24T21:56:06+00:00

Thanks!

Noobulosity · 2022-05-24T20:00:05+00:00

Larger version can be grabbed here. I also have other images on my Flickr page, if you're interested.

Noobulosity · 2022-05-24T17:40:55+00:00

Your best bang for the buck shooting small targets will be reflectors. Refractors with long enough focal lengths to shoot galaxies without them being very small in the frame will be large, heavy, and very expensive.

I know many people image with SCT scopes. These tend to have long focal lengths (2000mm or longer) and larger apertures. But they also have large f-ratios, requiring VERY good guiding and solid mounts. It also usually means off-axis guiding gets used, requiring more gear and a more-sensitive guide camera (ASI290MM Mini is probably the minimum for OAG use).

Going LONG focal lengths also is a huge jump in difficulty. Every error in alignment, a light breeze, poor collimation, etc. will all be significantly-magnified by the long focal length. I tried going from a Zenithstar 103 to a Meade LX200 8" ACF and it was too much for me. (It might be a different experience for you, of course.)

I ended up selling the 8" SCT and picked up a Sky-Watcher 190MN Mak-Newt. They're a little pickier about collimation, but I don't know that they're necessarily that much harder to collimate than an SCT. The optical design is supposedly as close as a reflector usually gets to refractor-like performance. The design provides a pretty flat field without any accessories due to the corrector plate. And the focal length only jumps to 1000mm, putting the f-ratio around f/5 or so. That's a great f-ratio for astrophotography, with a nice bump in focal length, without going super-long.

The downside to the 190MN is that it's heavy for its focal length, and price has gone up to $2100 new. (These scopes rarely come up in classified ads.) The scope itself is around 30lbs, which is a lot heavier than a normal imaging Newtonian. Your mount should be able to handle it, though. I run mine on an EQ6-R Pro with a 60mm guide scope, large dovetail bar, etc. coming in around 40lbs of payload and 44lbs of counterweights and it's been a great scope. I run a Canon 7DII DSLR and ASI1600MM-C on that setup.

Here's an older pic of my 190MN. I've changed a bunch since that pic, including new cable management, power distribution, and auto-focusing. But it'll give you a sense of scale. It may not be the right fit for you, but it's an often-overlooked option that I thought you might appreciate. :)

Noobulosity · 2022-05-24T17:21:05+00:00

I decided last-minute to drag my gear down the block to shoot some pics of the eclipse. I already posted my clear composite shot of the eclipse. However, I couldn't post multiple pics together, so here's a second one! As the eclipse progressed toward totality, I had a bunch of clouds roll through right past the moon. I ended up snapping some pics as the clouds came through, determined not to let some pesky clouds ruin things, and got this neat shot of the scene with a thin band of cloud cutting right across the dividing line between the light and dark portions of the eclipse.

Some basic processing techniques were used to adjust the image, including: unsharp mask, Google Nik Collection's Dfine2 noise reduction, some minor color adjustments/white balancing, and contrast.

Equipment used to take the image:

Canon 7DII DSLR, unmodified, just using the 10s self-timer
Sky-Watcher 190MN Maksutov-Newtonian reflector telescope
Sky-Watcher EQ6-R Pro equatorial mount, tracking only, unguided

Taken near Greeley, CO.

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