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i just can't decide

Kendo_Fuzzy

By Kendo_Fuzzy
in Imaging - Planetary

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Kendo_Fuzzy

Kendo_Fuzzy

Posted
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Hi everyone,

I am currently using a 250px Dob on an equatorial platform and using a Microsoft lifecam and other than the initial difficulty in getting my target in the imaging area I've been satisfied with the results considering the relatively low tech approach. However, I started off with a 130p goto which I was thinking of buying a 127 mak ota so that I could utilize it for various things. With regards to planetary imaging. Am I going to dramatically reduce my results trying this? Or is the benefit of using the goto mount going to improve my results? My other option was to think about upgrading my camera to something like the zwo 120 with a view to getting an eq mount for the ota. Any advice is most welcome

Fuzzy

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jambouk

jambouk

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How well does your current set up track a planet and keep it on the sensor? What is the focal length of the 250?

Any equatorial mount is going to struggle to take the 250, but it is done; i've done it, but it is a bit unwieldy.

The 127 is nice and compact, but i'm not sure it will offer you greatly improved data capture for planetary imaging compared to your current set up with a barlow/powermate.

A mono camera will always give better resolution.

James

James

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Kendo_Fuzzy

Kendo_Fuzzy

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Hi James,

Thanks for  the input

The 250 has a 1200mm focal length.

I realize that the investment in a mount is going to be as substantial as the size of it with the OTA on it :)

I'm completely tempted in going for the mono 120 with filter set and wheel but am concerned by the difficulties I would have using it on a non tracking setup.

Too many choices, if I had any hair I'd have pulled it out by now :)

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jambouk

jambouk

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Oh, i thought the dob mount was a tracking one. Sorry. That alters the balance.

The 127 is great for the moon, and good for planets, and some globular clusters, but for lots else i think is isn't the best instrument, though as always people do achieve great things.

The 250 has the benefit of great aperture. It really is a wonderful observing took as you know. Good for planetary imaging too if you can track it; either on an equatorial mount or on a tracking dob mount. For DSO imaging it is used, but again has some limitations, including coma, being large, potentially tricky to guide etc.

As you know, no one scope is good for everything. In an ideal world, you'd need an sct/mak for solar system imaging, a large newt for observing, and a short tube refractor for dso imaging. And a solar scope :)

Only you can make the call.

I would go for something which tracks first. Have you still got the okd tracking mount you could just get a 127 and mount onto?

I'm actually in wales now, bear Dolgellau.

James

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Kendo_Fuzzy

Kendo_Fuzzy

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Yes I still have the goto mount with the redundant 130 newt, so getting the 127 would be an easy option.

I'd rather not buy it if it's a backwards step imaging quality wise.

I can just about live with the slightly more faffy approach I've had to adopt on the eq platform.

Glad to hear you're living on the sunny side of the severn.

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jambouk

jambouk

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I'm not sure the 127 would be a step backwards. It's all a balance of different aspects. Aperture, inherent focal ratio, ability to track well, dew, need to collimate...

I personally think using filters and a mono camera on a non-tracking set up would be a right b@ll ache. But then i am biased as i can't even face filters with a tracking set up.

If you have a spare £200, get a 127 and stick it in the existing tracking mount. Use your current camera and see if you like the results. If not, sell it on, they sell pretty easily.

Or stay as you are? Can we see your results?

As you've realised you don't need to track for planetary but it does make life easier. A tracking mount will keep the planet on the sensor for the 2 minute imaging run.

James

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jambouk

jambouk

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Well that is very good! Roughly how many frames was that? How many times during an imaging run do you have to nudge the mount to keep the planet on the sensor?

I don't think you'd be getting greatly better images with the 127 - others may disagree.

James

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happy-kat

happy-kat

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You have a 250mm aperture scope with a 1200mm focal length.

Are proposing to get a 127mm aperture (and with central obstruction) with a 1500mm focal length.

Surely the increased apperature of the 250p trumps the smaller much slower 127 Mak at f11.8 and your scope is a light bucket at f4.8?

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Kendo_Fuzzy

Kendo_Fuzzy

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You have a 250mm aperture scope with a 1200mm focal length.

Are proposing to get a 127mm aperture (and with central obstruction) with a 1500mm focal length.

Surely the increased apperature of the 250p trumps the smaller much slower 127 Mak at f11.8 and your scope is a light bucket at f4.8?

I was hoping that would be the case but it was whether a Goto Mak 127 would out perform an eq mounted 250 Dob?

I think the answers are starting to come into view :)

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Kendo_Fuzzy

Kendo_Fuzzy

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Aperture [nearly] every time.

If you want to buy something, but an EQ mount. HEQ6 or AZEQ6 or equivalent. Even if you get fed up of trying to use the 250 on it, which you will, it will easily handle your next scope.

James

Thanks for the advice.

Now the 127 is ruled out I'm thinking that I'll improve my camera etc. and see how I get on, then add an EQ mount to complete the setup. then like you said see what the future brings :)

Many thanks for the advice

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happy-kat

happy-kat

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My very very inexperienced thoughts are that a 5x barlow is going to make a bigger grainy blurry image, I think a smaller sharper image would be much more pleasing just like at the eyepeice and it would be easier to find. You were creating a 6000mm focal length scope with f24.

So that you have a starting point why not image with what you have now but use maybe a 2x barlow.

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Barv

Barv

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Aperture is pretty much everything when it comes to planetary imaging and that little Mak just won't compare! If you can keep the image on the chip with the platform you really don't need to do much more. If it was me, I would go for the ZWO120 coloured cam as you can capture excellent images with that! Getting the initial image on the sensor takes practice but certainly helps if you have a well aligned finder or Telrad. A flip mirror is also a big help. Invest your money initially in a decent camera like the one I mentioned and maybe a flip mirror. I attach an image I took of Jupiter last year with a C11 and ZWO coloured cam.

Regards

Harvey

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hobsey

hobsey

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My main difficulty is getting the target in view in the first place, keeping it there during capture is a balancing act

I don't know how effective these are on a newtonian but have you thought about a flip mirror to help you get the image centralized to start off with?

http://www.365astronomy.com/365astronomy-imaging-flip-mirror-for-astrophotography-and-precise-focusing-p-3985.html

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