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04-09-2015, 05:22 AM   #1
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Astro/Nature Telescope Advice Please

Hi,

I have a Q 10 and have been looking at the Orion AC 80/350 StarBlast Autotracker, around 250, for both Astro and wildlife use (mainly sea birds I'm near the coast), I realise that combining these 2 functions is a compromise and that it will probably better at one than the other. It's generally cloudy around here so I expect the astro usage, which I would really like it for, will be a bit limited but here goes. There is also a 114/500 model for an extra 35 or so which I could rise to if it would make a substantial difference.

I was looking at a Dobsonion table top mount for it's convenience and this particular scope has a tripod mount as well, I have a heavy duty Giottos tripod and also a heavy wooden tripod I used to use with my construction level which can be adapted if necessary so I would have 3 mounting options.

I am a bit puzzled as to how the Q would be attached to the Telescope and how one would use it.

From reading most of the the astro sections it seems to me that you attach a C mount adapter and a 1.25" tube to the Q and insert this into the telescopes empty focusing mount which does not seem right to me as I would have thought you would attach it to one of the focusing eyepieces.

Advice on how the Q would actually be attached and how this attachment actually works and, as a telescope beginner, if I am heading down the right road would would be very much appreciated

Regards

CD

04-09-2015, 08:06 AM   #2
kwb
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Hi PenPusher,

QuoteQuote:
QuoteOriginally posted by PenPusher Quote
From reading most of the the astro sections it seems to me that you attach a C mount adapter and a 1.25" tube to the Q and insert this into the telescopes empty focusing mount
That's correct. There are more than one way to attach a camera to a telescope, and one of them is to use your telescope without an eyepiece as if it's the camera's lens. At the end of the day, your camera lens is just a (bunch of) lens(es) stuffed in a cylinder, right? Same thing for your telescope. This mode of operation is called prime focus, and you can think of the focal length of telescope as that of your camera lens.

In my case, I use Q-C adapter and C-T adapter, and it turns out that it doesn't focus to infinity as is. So I unscrewed the eyepiece adapter at the end of focuser, taped up the C-T to increase the diameter such that it becomes the snug fit for the focuser tube, and inserted the taped-up C-T directly into the focuser tube. See below.







Another topic is the choice of telescope, but I need to go to work now. Good luck!

Last edited by kwb; 04-09-2015 at 08:08 AM. Reason: photos somehow didn't show up originally.
04-09-2015, 08:13 AM   #3
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Location: New York
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QuoteOriginally posted by PenPusher Quote
...From reading most of the the astro sections it seems to me that you attach a C mount adapter and a 1.25" tube to the Q and insert this into the telescopes empty focusing mount which does not seem right to me as I would have thought you would attach it to one of the focusing eyepieces...
Either technique can work. The 1st highlighted portion, using the telescope as a big lens, is called "prime focus". The 2nd highlighted portion is called "eyepiece projection". Eyepiece projection can give more magnification by swapping eyepieces or adding extension tubes between the eyepiece and camera. That extra magnification also results in a darker image.

For astro usage, eyepiece projection works well on the moon and planets. Planets are tiny and need magnification, and they are still bright enough despite the darkened image. Deep sky objects (galaxies, nebula) use prime focus because they are already so dim that you need lots of exposure time.

The Orion Starblast scopes you are looking at are more for visual use than astrophotography. You should be able to get good photos of the moon, maybe decent photos of planets, and possibly photos of brighter deep sky objects but you won't be able to take very long exposures due to limited tracking accuracy. Astrophotography mounts are generally bulkier GEM (German Equatorial Mount) designs.

Note that astrophotography is rewarding but also a source of frustration many nights. On any given night it can feel like your gear, the weather, or your skills are fighting you. If you think LBA can be bad, what until you experience TBA (Telescope Buying Addiction). I recommend http://amzn.com/1554073448 for an intro to astrophotography. It covers general astronomy, gear, and techniques.

Last edited by DeadJohn; 04-09-2015 at 08:29 AM.
04-09-2015, 10:02 AM   #4
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Join Date: Apr 2009
Location: Ireland
Posts: 260
Original Poster
QuoteOriginally posted by kwb Quote
Hi PenPusher,

That's correct. There are more than one way to attach a camera to a telescope, and one of them is to use your telescope without an eyepiece as if it's the camera's lens. At the end of the day, your camera lens is just a (bunch of) lens(es) stuffed in a cylinder, right? Same thing for your telescope. This mode of operation is called prime focus, and you can think of the focal length of telescope as that of your camera lens.

In my case, I use Q-C adapter and C-T adapter, and it turns out that it doesn't focus to infinity as is. So I unscrewed the eyepiece adapter at the end of focuser, taped up the C-T to increase the diameter such that it becomes the snug fit for the focuser tube, and inserted the taped-up C-T directly into the focuser tube. See below.







Another topic is the choice of telescope, but I need to go to work now. Good luck!
KWB

Thank you very much, that clears up that mystery nicely, the taped up adjustment looks awfully like my DIY modifications to my shed dust collection system so I should be able to manage it.

Kind Regards.

CD

PS

I understand the need to go to work, retirement doesn't get you off the hook however, the She Who Must Be Obeyed has a never ending list of little things that need to be done which grows and grows.

---------- Post added 04-09-2015 at 06:12 PM ----------

QuoteOriginally posted by DeadJohn Quote
Either technique can work. The 1st highlighted portion, using the telescope as a big lens, is called "prime focus". The 2nd highlighted portion is called "eyepiece projection". Eyepiece projection can give more magnification by swapping eyepieces or adding extension tubes between the eyepiece and camera. That extra magnification also results in a darker image.

For astro usage, eyepiece projection works well on the moon and planets. Planets are tiny and need magnification, and they are still bright enough despite the darkened image. Deep sky objects (galaxies, nebula) use prime focus because they are already so dim that you need lots of exposure time.

The Orion Starblast scopes you are looking at are more for visual use than astrophotography. You should be able to get good photos of the moon, maybe decent photos of planets, and possibly photos of brighter deep sky objects but you won't be able to take very long exposures due to limited tracking accuracy. Astrophotography mounts are generally bulkier GEM (German Equatorial Mount) designs.

Note that astrophotography is rewarding but also a source of frustration many nights. On any given night it can feel like your gear, the weather, or your skills are fighting you. If you think LBA can be bad, what until you experience TBA (Telescope Buying Addiction). I recommend The Backyard Astronomer's Guide: Terence Dickinson, Alan Dyer: 9781554073443: Amazon.com: Books for an intro to astrophotography. It covers general astronomy, gear, and techniques.
DeadJohn,

Thank you, I was afraid that I was missing something and would end up having to acquire a couple of truck loads of gadgets to make it work.

I understand I have terminal LBA so TBA is going to be a new experience for the wallet, my Great, Great, Grandfather had something to do with the Telescope in Birr, (Parsonstown as it was called then) Co. Offaly, where the Milky Way was discovered, so I can see a yawning chasm forming in front of me.

I bought the book some time ago and shall have to read it again, probably several times.

Kind Regards

CD

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