SharpCap Forums

Same location. Bortle 6. Same equipment – Altair 66ED refractor, 0.8x reducer, Altair 183C camera. All images have similar capture times 25m (2018) v 30m (2019) v 30m (2019).

• Oct 2018: gain=400, black_level=50, exposure=100x15s, integration=25m

• Dec 2019: gain=200, black_level=30, exposure=30x60s, integration=30m

• 2019, better focus=tighter stars, less processing resulting in less tortured image, background not black, core not burnt out, retaining colour in stars (lost with the JPG).

• 2019 used lower gain, lower black_level, increased exposure. Black_level decided by shape of bias histogram. Increased exposure decided by histogram.

For comparison, I have added a longer exposure image taken the same night in Dec 2019.

• Dec 2019: gain=200, black_level=30, 15x120s, integration=30m. Better data due to longer exposure, more nebulosity, star colour evident, core starting to over expose (addressed with multiple exposures).

Dave

This was from Feb 2019 and has been reprocessed with Astro Pixel Processor 1.077 using the multi-session capability.
Altair 66ED refractor, 0.8x reducer, Altair 183M CMOS camera.
Session_1 data: 60x60s, 30 darks, Session_2 data: 100x4s, 30 darks. Plus 100 flats, 100 bias.



Some stars saturated, I was caught out by the sensitivity of the mono camera, maybe try 45s or even 30s and stack more (maybe 200). Plenty of fainter stars and not much black space between the Orion Nebula and Running Man.

Dave

Great work Dave!

Minos

Thanks Minos.

Dave,

It’s been awhile since I posted. After going through a defective mount (for more than a year, which was finally replaced) and struggling with my RI imager for another year, I finally decided that 5s exposures and consistent frustration wasn’t the answer. With the ongoing tutoring from a gracious friend in Australia, I’ve come to recognize (at least globally) that this hobby has a kind of common sense to it...I think I’m seeing the bigger picture.

After retiring my RI imager, I’ve decided to take all my frustrations out by buying a ZWO294 camera along with Hyperstar. I realize, in the words of Mark Twain, that the difference between an RI camera and a ZWO294, is like the difference between lightning and a lightning bug. However, my leap of faith has to do with my commitment to this hobby.

All that said, as I wait for my camera to arrive (the factory in China had to close because of the corona virus), I continue to read, study, and consult—all in preparation for my first night of imaging. So, long story short, here’s my question:

Psychologically speaking, on my first night of imaging, I need (hope) to be able to obtain a decent Live Stack and come away with an image that will say to me, “Yes! I really can do this!” This image doesn’t have to be a great image, just one that shows promise and hope for my astro future. I have a good handle on using the histograms, exposure, gain, and offset, but my simple question is how should I save my first attempt. I suspect since Live Stacking is my goal, that ‘save exactly as seen’ (PNG) would be the best way to get that first image. Is that right? Or is there a better, simpler way to save and reproduce that first image? Can’t wait to share my experience(s).

Clear Skies,
Joe

Joe

In Live Stack, from the Save drop down menu, Save with Adjustments or Save exactly as seen options provide a simple way to produce a single PNG file of the image shown at the time.

Good Luck!

Dave

Do we know what Joe's field of view will be?

Evolution 8 I think Brian.

Good luck, Joe! Having made the same transition (RI to 294MC Pro) a while back, you are in for a real treat! The ZWO camera is so much easier to use with SharpCap -- no more going through separate obtuse menu settings outside of SharpCap to set exposure and gain, much wider field of view making it easier to find stars for alignment and for fitting larger objects in the frame, much better resolution, lower noise, etc. i can't remember if you have a Celestron 0.63x reducer/flattener, but I highly recommend you getting one if you don't. Use that in place of the cheap 0.5x reducer that came with the RI.

With the 0.63x reducer/flattener installed, plus a Celestron T-Adapter and the included 21 mm and 16.5 mm extensions (and the 11 mm extension ring that comes installed on the camera) to obtain the 105 mm backspacing required for the Celestron 0.63x reducer, the field of view is just enough to image a full Moon in its entirety. Just be aware that with this configuration, you will be limited to objects below about 60 degrees in altitude; otherwise the camera will hit the mount. For imaging objects higher than that, I've used it with a star diagonal to avoid the mount obstruction issue. Of course, with no reducer, the OTA can be moved forward on the dovetail to also avoid mount collisions.

I think you will find that this camera (yes, an equipment purchase) will vastly improve both the results you will get and the experience you will have while doing it over the RI (provided of course you have taken the time to get the basics of aligning your mount, focusing, and using SharpCap down).

Joe mentioned HyperStar. Doesn't that put the camera in front?

According to Celestron the Evolution 8, out of the box, has an aperture of 203.2mm and focal length of 2032mm. Starizona's website says that HyperStar will convert it to f/2 which will put the effective focal length at 406.4mm. The ASI294MC Pro's pixel size is 4.63um and matrix of 4144x2822 pixels.

According to the CCD Suitability calculator the camera will under-sample with "OK Seeing" conditions. Living where he is, Joe is most likely to encounter "Poor Seeing" conditions which puts him in the green zone. (Basically his scope/camera is similar to mine with respect to under-sampling. After working with my scope/camera for over a year, if I were to do it over again, I would choose a camera with a smaller pixel size or a scope with a longer focal length.)

According to the Field of View calculator his FOV is 2.7 degrees x 1.84 degrees. Here is how M42 should frame up:
The calculators can be found here:
https://astronomy.tools/calculators/ccd_suitability
and here:
https://astronomy.tools/calculators/field_of_view/

Let me know if I've made an error.

Brian