Difficulty with Mars

[azkaz (Aaron)]

Morning all!
I am a noob still with AP and am having difficulty with Mars.

I can track it no problems but the image is only the size of a pinhead on my screen. Setup is Heq5Pro, ASI120mc-s and Sharpcap.

After taking a 3 min video and loading it into Registax or Autostakkert, the processing fails. ASK2 says "all frames were rejected try cropping the image size" and Registax just fails all together.

So I tried adding a Televue 2 x barlow into the image train, hoping that would provide a larger image on the sensor, but then was unable to get focus. I couldn't even find it on the screen. Even on the moon, I could see light (it was HUGE) but I couldn't wind the focuser out enough to get focus.
So obviously I'm missing a few things here.
Could anyone pass on there experience with these issues.
Greatly appreciated.


I have attached an image of my image train with the barlow. The barlow isn't in the focuser properly as i was trying to to get a few more cm of range from it.

[Mickoid (Michael)]

Merry Christmas Aaron, welcome to the frustrating world of planetary photography! First of all, you're making it really hard for yourself trying to shoot Mars now. Since opposition in late July, it has been receding and phasing to a gibbous state, reducing in size considerably. Only the largest of instruments would show any detail on the planet so don't be surprised at the size it was on your sensor. Even introducing a 2X Barlow would hardly make it worthwhile.

Sounds like you don't have enough back focus using the Barlow to achieve focus. Sometimes, depending how far out it is, you can just move the Barlow or camera out a bit from where they seat in the holders. As long as they still hold securely. This may be just enough to enable you to achieve focus.

One thing you could try with what you already have on Mars is to process the video footage in a free download called Pipp. It allows you to crop the video frame so that it only registers the area of interest and not all that blackness you have around your image of Mars.

Good luck! Keep trying, with perseverance and experimentation, youll eventually get there!

[azkaz (Aaron)]

Thanks for the support and advice
Yeah, I just thought, I have a planetary camera, there is a planet, let's shoot it!! I understand what your saying.
I have pipp, I will give it a try! I am able to process a ROI in Registax I think, but that didn't seem to help when I boxed around the small dot of Mars.

I had every mm of extension in use with the barlow and focuser wound right out, but still couldn't get a focus. Maybe an extension tube available on Bintel would do the trick? It's getting pretty long though with all that in place.

Thanks.

[Rigel003 (Graeme)]

Mars is about 8 arc seconds at the moment as opposed to 24 at opposition earlier in the year. Still worth a try though.

In Sharpcap, find and centre the planet using full frame and then reduce the ROI to as small as you can. This will increase your frame rate enormously. No point in capturing lots of black space around the object and this makes an easier job for the processing software. Sounds like you need an extension tube to reach focus with the barlow and with this target you'll definitely need it. When you add the barlow to the image train it's common to have trouble finding the planet again on screen, even though it was centred before. Make sure you change back to full frame initially and boost exposure and gain. Then work with focusing which changes a lot. When iMars is reacquired and centred, then go back to the smaller ROI and adjust gain and exposure.

Finally, are you absolutely sure that's Mars you have there? From the screen shot it's not at all reddish and looks like it could possibly be a star. Have you checked it out visually first?

[azkaz (Aaron)]

Thanks for the reply, I appreciate your suggestions.

Yes, definitely mars, it was just the view in the software before debayering.

I have multiple videos saved so I will continue to play around with it as you suggested to see if I can pull anything out of it.

[mental4astro (Alexander)]

A little word of caution here: be careful with loading the focuser too much - this goes for both items you hang off it and how far out you pull the draw tube. The focuser will flex, the draw tube will sag down, and the chain of gear may not be rigid enough to all keep dead straight. The result will be a poor image as effectively the whole optical chain is out of whack! And you may just be pushing the proverbial uphill. Keep an eye on the integrity of the optical chain. Unless it is secure nothing else you do will improve the image quality.

And over tightening set screws is not the solution either. This just over strains threads (aluminium is very soft), and items can become damaged. Never over tighten set screws. If you need to do this to make things straight, use it as a guide that's telling you things are not good and that you need to change things. There's a lot of over tightened set screws I'm sure in the set up you've posted. And over tightening also doesn't leave things dead straight either as there will be some play between itmes too.

Alex.

[azkaz (Aaron)]

Thanks for the input, you suggestion to use my diagonal to add length to my focal train is excellent. Looking forward to trying it out at the next opportunity!

[mental4astro (Alexander)]

To try out your new optical train with the diagonal, an easier target than Mars is the Moon along its terminator. A lot of detail there, and a severe task master!

Alex.

[gb44 (Glenn)]

Aaron
What is that in your optical train after the barlow and attached to the camera?
The nosepiece of the camera ought to disappear into the barlow.

GlennB

[azkaz (Aaron)]

Lo, it goes 2 x barlow, then the required back spacing spacers that ZWO have for their cameras. It was just a quick test with everything just secured to see if I could get the extra length to get the camera to focus with the barlow.

[gb44 (Glenn)]

Aaron
I have a 178MC and have good results using 2x barlow. I just put it straight in the barlow. For 4x I have just stacked two barlows.
Have another try without that spacing.

All I can see in the ZWO specs is the back space of 12.5mm for my camera.
From the pic it looks like your camera chip is about 30mm from the barlow aperture. This doesnt make sense to me... maybe I'm missing something?
I have seen no diagram that suggests this spacing, so it might be THE problem.

Cheers
GlennB

[azkaz (Aaron)]

Oh my goodness, thank you so much.
I "heard" and didn't confirm myself that the back focus on the 120 and 294 was 65mm.
Shame on me for not checking.
The 120 is 12.5mm and the 294 is 6.5mm.
Lesson hopefully learnt, thank once again for the suggestion.!!!: thumbsup: