SharpCap Forums

Hi Brian,
Very generous of you offering up the support information.
I’ll look at that app over the weekend. I did mention in an earlier post Bortle 7.5, so I would say for the moment that would be ok, I’m literally on the border of some foothills heading into the mountains so it gets darker with each mile.
By the way my wife and I were up in the sierras a couple months ago and I brought a tripod and my Astro binoculars.
Absolutely stunning without binoculars, with, almost looked artificial. Altitude around 6000 feet. It’s nice being so close. Perhaps one day I’ll take my gear up there.
On the other note, I don’t even bother setting up if I don’t have a clear sky from 5:30 for a few hours. Even with that, I had to cut things off as the fog layer showed up within 15 minutes of my last check. It now looks like next Friday as next viable session. We haven’t had weather like this for 5+ years and need it so I just have to be patient. I also did some more reading regarding the long exposure times and it’s making more sense. Thanks again for that callout and all the input.
Frank

Hi Brian,
I installed the app and took a look. Figured I’d do it now.
I seem to be on the border of 6 and 7, so I guess 6.5 bortle?
Better than I thought.
Frank

Hi Frank,

At Bortle 6.5, with the SpaceCat at f/4.9, and the ASI2600MC at Gain 110, your minimum exposure is 3.3 seconds. To be safe I would round it up to 5.0 seconds.

What's meant by minimum exposure? It is the exposure at which "dark" space produces good, stackable signal per pixel. Going below that puts you into "photon starvation" such that the signal can't overcome noise, therefore you lose faint nebulosity that you could see otherwise.

The calculation I'm using is the exact same one that SharpCap uses. I think you will be pleasantly surprised with M42. You should only need about 30 minutes of integration time.

Brian

Thanks Brian.
I will definitely give this a go.
As mentioned I have a little time before I do M42.

I plan on doing another session on M33 in the meantime when conditions are favorable with a shorter exposure.
Given that, what would you recommend with the latest information?
Also, one thing that occurred to me after reviewing your posts was the moon. That night it was about 50 percent and very close to overhead. I’m sure it affected the session.
As always, thanks!
Frank

Hi Frank,

Beware the Moon. Essentially it takes your Bortle 6.5 skies to Bortle 8 (city skies). As you get further into this hobby you'll learn to salvage moonlit nights with a narrowband filter...until then, patience. So, yeah, your M33 never had a chance between the Moon, fog, and 3-minute exposures! Honestly, I'd discard those frames and start anew.

By the way, you can use that 5-second exposure for any object from your home, however if you travel to the Sierras, let me know and I'll redo the calculation for the darker skies you'll find there. Darker skies require longer exposures. Beware that if you use a 5-second exposure in the Sierras your camera will suffer from photon starvation.

If you are looking for other objects that pique your interest you are welcome to use my web app at:
https://briandavidmorgan.com/demos/astr ... ip-planner

Scroll to bottom to find the calculator but I'd recommend reading about it first.

From the dropdown, select "List suitable astrophotography targets for a specific time window..."
The query window will fill with the query:

List suitable astrophotography targets for a specific time window tonight.

Home base: {your town here}
Date: {e.g., December 13, 2025}
Time window: {e.g., 23:00-02:00}
Direction: {e.g., east, southeast, due south, any}
Minimum altitude: {e.g., 30 degrees}

Preferences: {clusters, galaxies, nebulae, anything interesting}

Please include:
- A list of targets visible in that window in that general direction
- Approximate best time and altitude for each target
- Angular size of each target so I can judge whether it fits my rig

You can immediately press the "Ask" button. It'll think for several seconds then respond.
However for it to be useful for you, replace this line:

Home base: {your town here}

with your town and state, for example:

Home base: Los Angeles, CA

click "Ask" again and wait for the response.

The database is quite large. The list is sorted by catalog name and object number: first "IC" (Index Catalog), then "M" (Messier) and then "NGC" (New General Catalog).

Scroll down to where the Messier objects live. The printout lists only those objects that are above your horizon during the time window you specify. Each summary line has a Details button where you can view a Wikipedia object image. Be warned that these are Hubble Space Telescope images, so they look way better than what we can obtain with our equipment.

If you have any questions, just ask.

Brian

Great information Brian!
I’ll keep you posted as I progress and will indeed check your app out.
Thanks!!!
Frank

Frank

Have a read of viewtopic.php?t=596 for an account of my journey to date. Page 5 was when I started to make real progress - dates from 2017 - 2024.

M42 - remember this:
Starting out - M42 is an easy object because it is big and bright.
5 years later - M42 is a difficult object because it is big and bright.

Enjoy the journey (and the bumpy ride).

Dave

Thanks Dave, I will check it out.
Eager to get out late next week. Looks like 3 evenings will be great although the moon will be at about 50 percent.
Getting a lot of direction from forum members. It’s a great group of folks!
Frank

Frank

I was out last night, under a very bright full moon. First up was M33. I ran a test of 30x10s with an L filter. A single FITS frame was washed out, so I switched to an Ha filter.


This is the result of an Ha stack of 10x450s.


All the Ha regions are the red parts of this image https://astrobackyard.com/m33-triangulum-galaxy/
To get this effect with your ASI2600, a dual band Ha/OIII filter would be needed. The Ha can then be extracted and processed separately.

Some background for the minimum exposure technique that Brian mentioned viewtopic.php?t=8322

Dave

Thanks Dave.
Looks good. Hopefully I’ll have something to post sometime next week. Conditions for the evenings are looking better and I might have a few nights to choose from.
Frank