Mak127 and ASI120MC

[ezio49 (Ezio)]

There is also thisone. It is a terrible Seben, but if I use it only as extener I suppose it could be a ceap solution.
Your opinion?
http://www.amazon.it/Seben-Lente-Bar...4662912&sr=1-2
Ezio

[Screwdriverone (Chris)]

Hi Ezio,

I wouldnt recommend a cheap barlow if you are trying to get some reasonable results with the Mak and the ASI camera. You will get horrible colour fringing on the planet as cheap barlows will refract the light wavelengths differently for each colour.

Your best bet is to start with a 2 x or 3x Televue barlow. I use a Televue 5x barlow with my F5 (1000mm Focal length) skywatcher newtonian reflector to effectively give me F25 and my Imaging source DBK21AU618.AS webcam but with the longer 1500mm focal length of the Maksutov, you probably would be better off with a 2 or 3x magnification to give you F22 or F33 (F33 might be pushing it too far for the seeing (atmospheric turbulence))

If your camera comes to focus with only the barlow in (and NOT the diagonal, dont use this!) then you shouldnt need the extension tube at all.

Otherwise, you would put the extension tube in the telescope focuser first, then the barlow and then the ASI camera and see if that comes to focus. The extension tube is effectively replacing the diagonal in the image train, so you might need that distance in order to simulate the distance the light would normally travel through the diagonal.

There have been some lovely images taken with the ASI cameras lately and I am sure the MAK should do a nice job on planetary, even if it is a modest 5 inch aperture, so give it a go!

Cheers

Chris

[ezio49 (Ezio)]

Chris,
thank you very much.
Your suggestions are very clear and solved a lot of my doubts.
At present I have a Celestron OMNI 2x Barlow. Do you think it is acceptable, at least for the beginning?
About the low cost Barlow that I supposed to buy, my idea was to remove the lens and to use it as an extension tube. I have seen on several vendors sites that a very low quality Barlow costs less than an extension tube. Could be their body is in plastic..........
Ciao
Ezio

[kelemenlajos]

Hi Ezio!

Sorry i didnt got any email alerts from your post after mine on 03.31 till the last two.

For the neximage, i don't know. I read that asi is better but didn't found any comparison.

For the barlow: if it can be disassembled, then anything is good, go for the cheapest, and throw away the optics

Originally Posted by Screwdriverone

Hi Ezio,
Your best bet is to start with a 2 x or 3x Televue barlow. I use a Televue 5x barlow with my F5 (1000mm Focal length) skywatcher newtonian reflector to effectively give me F25 and my Imaging source DBK21AU618.AS webcam but with the longer 1500mm focal length of the Maksutov, you probably would be better off with a 2 or 3x magnification to give you F22 or F33 (F33 might be pushing it too far for the seeing (atmospheric turbulence))

Hi Chris, your right on this, but Televue 3x is 3 times more expensive than the gso, and it's isn't 3 times better. So it's Ezios call to choose.

Originally Posted by Screwdriverone

If your camera comes to focus with only the barlow in (and NOT the diagonal, dont use this!) then you shouldnt need the extension tube at all.

Please read the previous posts. I didn't wrote anything about it's needed because of not using the diagonal. It's 50% about comfort, and 50% about not getting frustrated.

Originally Posted by Screwdriverone

so you might need that distance in order to simulate the distance the light would normally travel through the diagonal.

This is theoretically right but with MC-s you didn't got the same focusing problem as with Newtonians. The MAKs got so much room in the focusing, that you could add a 30cm long tube, and still can get focused image.

Originally Posted by Screwdriverone

There have been some lovely images taken with the ASI cameras lately and I am sure the MAK should do a nice job on planetary, even if it is a modest 5 inch aperture, so give it a go!

Yes and with a DSLR it's capable for DSO imaging too Ezio, but don't expect too much:
http://www.astrobin.com/15626/
http://www.astrobin.com/15630/
http://www.astrobin.com/15631/
http://www.astrobin.com/37278/
The weakest link for dso is your mount.
The images i have done are with eq5 + ra motor (and with precise polar alignment).

[ezio49 (Ezio)]

Lajos and Chris,
Thanks Alain for your suggestions.
The pictures you linked are very nice. I shall be happy to reach these results.
So, I am almost convinced to buy the asi120mc.
Have a good day.
Ezio

[Shiraz (Ray)]

Ezio. The asi120 has fairly small pixels and you should aim for about f19 - in combination with your scope you will only need a 1.5x Barlow - a 3x Barlow would give you 1/4 the sensitivity with no additional resolution. Even a 2x is a bit too much magnification. start off without a Barlow maybe

[ezio49 (Ezio)]

Originally Posted by Shiraz

Ezio. The asi120 has fairly small pixels and you should aim for about f19 - in combination with your scope you will only need a 1.5x Barlow - a 3x Barlow would give you 1/4 the sensitivity with no additional resolution. Even a 2x is a bit too much magnification. start off without a Barlow maybe

Shiraz,
my idea was to start installing the camera directly on the telescope and later to use my 2x Barlow. In case it is needed (depending also by the results I shall be able to reach) I shall buy a 1,5 x. Initially i shall start with 640 x 480 resolution, also because I have a lot of old computers that probably shall not be able to manage high speed (i.e. 70 fps).
They are:
a desktop with AMD Athlon ™ 64 X2 dual core processor 3800+ - 4GB RAM – Window Vista
a laptop with Intel Pentium M750 and 500MB RAM-Window XP
a netbook with Intel Athom and 500MB RAM - Window XP
As you may see its a lot of machine but their sum does made a good machine at all.
Ciao
Ezio