No stars no first light

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No stars no first light

Post by arrowspace90 » Mon Feb 17, 2020 2:53 pm

Last night I tried for the first time to set up my accumulated new rig. I have a Rasa 8, a EQ6R, and ZWO main and guide cams (533/290).

All of this stuff was powered on. I started SharpCap on the laptop and the program opened normally. SC "saw" both my cameras, so good! Thinking in terms of proceeding to focusing the cameras and attempting a polar alignment, I selected the guide cam.

I saw nothing but black. Uh-oh is this thing really turned on? It occurred to me that I might be badly out of focus (I have no experience with astro photography). So I moved the small guide cam back and forth in the barrel of the guide scope, hoping to see stars. But there was nothing but black.

I switched to the main cam. The ASI 533 has a square format and I saw this difference on the screen. But all was still black.

Ok, now I had NOT made any inputs to the camera settings. Without doing this, is it likely that I would see zero? I perhaps mistakenly thought that I would first see a blurry picture, then go to work on improving what I saw. Should I have instead began with some gain settings and exposure settings?
This newbie was clueless. If I try this in the daytime, should I at least see brightness? Blue or clouds? What do I need to type in?

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Re: No stars no first light

Post by admin » Mon Feb 17, 2020 9:08 pm


Basically you're facing the steepest part of the learning curve in astrophotography – getting your first image out requires you to get three things right at the same time – pointing the telescope in the right direction, focusing and camera settings. I would always suggest using the moon as the first target as it is big and bright and can make all three of these things easier (you have a good chance of seeing it on the camera even if your settings are wrong and you are out of focus – with stars you have to be close to focus and have decent settings to even see anything).

So, first steps would be to aim for the moon, turn up the exposure to maybe 0.5s and turn up the camera gain as well which will help you spot the bright nimbus around the moon even if the moon is just out of view. Once you get the moon in view, you can turn down the exposure until it's no longer washed out and then adjust the focus position until you start seeing a crisp image. Finally you can move away from the moon and start looking for stars by turning the exposure backup to a couple of seconds and the gain up towards middling to high levels.

Hope this helps, Robin

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Re: No stars no first light

Post by BlackWikkett » Tue Feb 18, 2020 2:56 am

I've only been at this hobby since 2017 and early days struggle is still very fresh heheheh. You may also try a rough focus during the day. Point you scope at a distant object the further away the better. You'll want to turn the exposure and gain way down. The RASA is a very fast scope so even once you get the focus close you will not need very long exposure. With the ASI533 try 5-15 sec with about 200 gain once you have focus and your trying to image at night.

Day time focus try 1 sec exp. and 200 gain. You should see something other than black screen. If still nothing remove from scope and see if you're getting something.

Good luck!

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Re: No stars no first light

Post by turfpit » Tue Feb 18, 2020 9:30 am


I usually try and set-up (or test new equipment) during the day. Be careful of the sun. The mobile mast setup was done during the day and the second image at the end of the day - both objects are about one mile away. I take the opportunity to ensure the red dot finder (or finder scope) and telescope (centre reticule) are both pointing at the same place to make the mount alignment process more accurate. As the light fails, a more accurate focus can be obtained using the street lights. Note the exposure of 1s - you probably need less with the RASA.

mobile-mast.JPG (12.42 KiB) Viewed 103 times

setting up 2.png
setting up 2.png (632.53 KiB) Viewed 103 times

A focus like this would be accurate enough for mount alignment. For accurate focus prior to imaging deep sky objects a Bahtinov Mask can be used ( a forum search will point to some articles on this).

As Chris rightly states, starting off in this hobby can be an extremely frustrating experience. If it is possible, try setting up the scope in the house and practise during the day - I made my best progress that way.


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Re: No stars no first light

Post by umasscrew39 » Tue Feb 18, 2020 11:42 am

In addition to the great advice already received, if you cannot wait for a bright moon or have time during the day to test things, turn your RASA 8 towards the Orion nebula. Given your scope and the ZWO ASI533MC Pro, M42 will fill up the field of view very brightly (try 200 gain, 10 brightness, 20s exposure). I have the 533 and it may not be the best first camera to try given it is a relatively small sensor (40% less) next to more common cameras like the ASI294 or 1600. However, it is an excellent, very low noise camera with no amp glow. So, just keep at it as getting the scope aligned to point at the object of interest, followed by focusing are always the toughest things to do at the beginning. Also, if you do not have a planetarium program, you may want to consider one (like SkySafari 6 Pro) to help guide you through the night sky.


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