Not Getting Far - Need HELP!

[DRCORTEX]

Hi Peoples,

I am starting to rip what is left of my hair out trying to get into some simple live view.

I have a CPC800, GSTAR-EX3 camera, Starsense, Celestron Focus Motor, CPWI, and Toupsky.

I have been using Alpha C, to try to get the focus, and the attached are the closest I can get. To much one way, a doughnut, to much the other, just a blob.

I have a F/6.3 focal reducer coming, not sure if this will help, but worth a shot as the scope is F/10 on a dual form Alt/Az.

Now I understand, that I am not going to get those eyewatering shots I look at. All I really want is live view, with a few snaps, and maybe a few stacks, all limited to 30s or so.

Could someone comment on these shots ? Maybe you have an idea as to what I am doing wrong. I have spent hours on this. The collimation of the SCT seems fine - doughnuts are nice and even ( see EX4 )

They were taken as a snap with 5sec accumulation at 50 gain and a gamma of .43

Anyway, worth an ask. Looking forward to your input

Cheers,

Doc

Thank

[bojan]

So... what is the problem?
On the image you attached, I see an overexposed star, pretty much in focus...

[DRCORTEX]

Thanks,

Will try again tonight, adjust camera settings. Do you have any recommendations ?

Regards,

Doc

[bojan]

Well no.. or - it all depends on what you want to achieve.

[Outcast]

I concur with Bojan, it just looks over exposed...

Try experimenting with exposure times (ie: shorter) with the current gain setting you are using or, alternatively, reduce the gain setting...

Keep shooting with different settings until you achieve the results you are looking for, to be honest, it's pretty much how we all get started & results in as getting to know our camera settings in such a way as to be able to apply them according to what the target is...

As Bojan has indicated, settings will vary depending on what you want to shoot... Lunar, big bright planets will require shorter exposures or lower gain settings to something in Deep Space which is significantly dimmer.

Assuming in your picture you have used a bright star, so a reduction in either exposure time or gain settings should yield better results...

You will however, experience some 'blobbyness' of stars when shooting with an SCT, even with a focal reducer...

An example is attached... M42 taken through the 8"SCT I used to own...

Sorry, there are no magic number settings to give you, just the advice to play around with the settings til you achieve the result you are looking for & then accumulate that experience & knowledge & apply it to other targets in an iterative way...

Cheers

[DRCORTEX]

Cheers, yes, a long learning curve, to be expected. I was speaking to David Lloyd today, gave him an example of my collimation. He advises it is out a bit according to telescope circle, so I will try adjusting at first dark, and gain, exposure, etc. Long as it is from a comfortable position.

My F/6.3 corrector arrived today, so that will also be an interesting test.

Two steps forward, one step back :)

Let you know what I find, then more questions.

In the end, it is live view I am most interested in, a snap here or there. I like the concept of live view, no cold nights, bad back, bending over an eyepiece for more than 15mins, causes me nothing but grief.

The live view sites, tend to be a bit pricey

Cheers,

Doc

[h0ughy]

To be honest if you are finding focus I would recommend a bahtnov mask https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.deepskywatch.com/Articles/make-bahtinov-mask.html&ved=2ahUKEwigjtOHg-roAhVGxzgGHRCPA78QFjAHegQIBRAB&usg=AOvVaw2nSeQKLHWtLS-XILVPT15P&cshid=1586939713568

I manually focus my Scopes, sad I know but I want to get it right. Even for me it's an easy solution and I use the celestron focus motor control using APT and the celestron focus software. With the magnifier over a bright star it is very simple. Note I do set the focus steps to 1.

[Sunfish]

Try something easy and hard to miss and with interesting detail, like the moon , Jupiter , M42 or Carina. The reducer will mean you can fit the moon and a larger field in . Avoid bright stars except for focusing as there will be too many reflections. I started with a DSLR tilt screen which was much easier and always gave a result.

[barx1963]

Doc
First off I can make a couple of comments. Collimation is one of those topics that newcomers to our hobby get stressed out about. If you look at some info in the web, you would get the impression that not having perfect collimation will cause disruption of the space-time continuum. My advice to beginners is "get it as close as you can, without spending more than a few minutes or at the most an hour, then forget it and learn to use your scope". Collimation really is a case of diminishing returns, there are better things to spend your time on. While I understand you want to do live viewing, a few hours at the eyepiece will serve well in this situation. Just pointing the scope at the sky, look in the eyepiece and play with focus so you understand how focus works on your scope will pay dividends. As an added benefit, if the stars are reasonably sharp visually, you can put collimation out of your mind until you need to. When I started using an SCT, I quickly found out that "the moon is your friend". You can go out on a nice moonlit night and easily line up and work out focus and how the settings on your software and camera work.

Malcolm

[DRCORTEX]

Hi All,

I have played around with the Hubble Artifical star indoors for collimation, using Telescope Circles.

It looks pretty well spot on in Telescope circles

I then did a 10s stack of 10 frames of Omega Centauri ( see attached ). I didn't spend too much time on the image at this point.

I still don't seem to be able to obtain a pinpoint image of Alpha Centauri, same thing doughnut becomes clearer, reaches the focus point ( a blob ), then starts to defocus again as you move further inwards or outwards as the case may be. This is using a Celestron motor focuser at rate 1.

I have ordered a Bhatinov mask, to see if that helps.

My next questions are - could this be due to heavy light pollution, or perhaps the camera is not quite the distance it needs to be from the visual back ? Is there a way of determining exactlly what this distance should be using an F/6.3 reducer ? I must admit, the wider FOV the reducer delivers, does make things just that little bit easier.

Cheers,

Doc

[bojan]

Omega look very much OK to me..

As to alpha Cen, it is very bright object, so you need much shorter exposure/lower ISO (or both) to get it look sharper.

[DRCORTEX]

OK, getting just that little bit better.

Managed the Carina Nebula and colour is totally wrong, but think I am on the right track.

Next, I think I need to research how histograms work, and what they can tell you.


Cheers,

Doc

[ChrisV]

+1. Omega centauri looks pretty good. The bahtinov mask will certainly help. Don't worry about colour - all in the processing

[DRCORTEX]

Thanks for that.

I was quite amazed that I could actually get an image, and all from my kitchen table.

Post processing, well, thats another story altogether. I havn't even touched on it yet. Still playing with the GSTAR-EX3, fiddling with this and that.

My ultimate aim, probably a hyperstar, then a wedge, and a good single shot colour. That is a long way down the track. I don't see the point in jumping into more expensive addons, when I don't understand what I already have.

Cheers,

Lance

[appiice]

Hello Doc

I know others have mentioned a Bahtinov mask, I have a Celestron 1100 Edge HD and really struggle trying to focus manually, the mask in my view is the only way to go, younger eyes may be able to focus but not mine, I also have a ED72 that I use as a guide scope, I was having trouble with focusing that and looked on-line and found a site that has templates that enable you to cut your own mask.

It was quicker to print a template out and stick that to a plastic cover off the back of a sketch book, 1/2 an hour later I had a mask that fitted and cost almost nothing.

http://www.deepskywatch.com/Articles/make-bahtinov-mask.html

Just my 2 cents worth.

Ed

[assbutt94]

After you've taken an image on your camera, and you can view it on your rear screen, you should be able to press an "info" button or something similar, to cycle the information shown about the photo you are viewing. It varies camera to camera, but pretty much every dslr should have this feature and it should allow you to view a histogram of your image.

This link has an example of how histograms may appear https://i.pinimg.com/originals/2c/ce/56/2cce5681cc10e026b1e0f25834a25a29.jp g.

The histogram can show how much of your image is exposed to what amount.

Since most of the night sky, generally speaking, is dim/dark, trying to aim for an exposure with a histogram thats slightly left of center as a good starting point.

If the histogram peaks to the far left, try capture more light with a longer exposure or faster f/ ratio (like when using a focal reducer).
You may not be able to get exposures long enough to achieve the histogram you are aiming for, but just do the best with what you have.

Dont worry so much about purchasing new equipment, get the feel of what you currently have first. A bahtinov mask will be very helpful though, as will a focal reducer.
Colimation can really help get finer details, but if an out of focus star in the middle of the view shows a concentric donut its probably close enough not to worry about for now. Collimation wont help much if focus is off.

[DRCORTEX]

Thanks everyone for all the good advice. Seriously considering the Hyperstar as an alternative to a RASA. I really like the idea of switching from a visual F/10, to a F/2 by replacing the secondary. If I wanted to two scopes, then the money really piles up.

Not that keen though on adding a wedge based on things I have read.

My thoughts are, I should be able to get say 20 second exposures, and stack them, then post process.

Has anyone here used the GSTAR-EX3 with Hyperstar ? If this works out, then I will look at a better quality one shot colour CMOS camera.

I realize that without guiding and a wedge, I won't get those very dim fuzzies, but it should increase my range of targets quite appreciably.

The Hyperstar sounds good also, as I simply don't have that time to take heaps of long exposures. Have to work as well :P

Could people give me feedback I what I propose - have saved the money, and a burning desire to spend it :)

Cheers

Lance

[h0ughy]

To be quite blunt no you won't change the hyperstar setup because of how difficult it is to collimate in its hyperstar format and when you change it back to f10.
You're never going to have the perfect scope setup. There are always trade-offs. Best all-round scope would be a large refractor with a reducer flattener or buy a Barlow to use for planets.
Everything has a cost.

[DRCORTEX]

[QUOTE=assbutt94;1471115]

This link has an example of how histograms may appear https://i.pinimg.com/originals/2c/ce/56/2cce5681cc10e026b1e0f25834a25a29.jp g.

Now that is useful info - thanks

[DRCORTEX]

Market hype - easily convert from on to the other, takes 2 minutes. I wonder if any consumer affairs bodies investigate a very lucrative astronomy market

[h0ughy]

Like most things yes you can just swap it out in under a few minutes. That is true.

But will it be right :lol:
Possibly not.

Scopes are like golf clubs, you need the right one to achieve what ever floats your boat.

[DRCORTEX]

And then, what boat - lol :) - collimation dosn't scare me - it certainly used to. I find the Hubble articifical star and telescope circles a big help, but I hear that with the Hyperstar, collimation is just that bit trickier

[DRCORTEX]

I can certainly relate to that, it caused me no end of hassle when I began with a Dob. Eventually, it became easy enough, the secondary was always my bother. With an SCT, theoritically, you never need to collimate the primary.

The hubble artificial star really helped me big time, no drift, use it during the day. I find it far easier to collimate an SCT.

Cheers,

Lance