First telescope, which one should I get?, page 3
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reply posted on 14-10-2011 @ 02:52 PM by Hellhound604
reply to post by camaro68ss


some great advice in this thread. I just want to add one more, if you look for a newtonian (most Dobsonians are Newtonians), just be careful of some marketing hype. Don't go for an F4.0 scope, as you will spend a lot of time collimating it. All mirror telescopes, esp. fast Newtonians need this. If you rather go for a slower like F4.5 or slower scope, the collimation is much less critical. (I am speaking now from memory, had my F4.0 telescope long time ago, but to get acceptable results, all the mirrors had to be aligned to something like 0.5mm!!!). great if you have the time AND you bought a collimator with the telescope.

The F-ratio of a telescope is NOT like the F-stop of a camera. The focal ratio of the telescope is the focal length divided by the diameter of the mirror, i.e. a 200mm mirror (8") with an 800mm focal length will give you a F4.0 telescope
edit on 14/10/2011 by Hellhound604 because: added the last part



reply posted on 14-10-2011 @ 06:06 PM by lbndhr
Originally posted by Hellhound604
reply to post by camaro68ss


some great advice in this thread. I just want to add one more, if you look for a newtonian (most Dobsonians are Newtonians), just be careful of some marketing hype. Don't go for an F4.0 scope, as you will spend a lot of time collimating it. All mirror telescopes, esp. fast Newtonians need this. If you rather go for a slower like F4.5 or slower scope, the collimation is much less critical. (I am speaking now from memory, had my F4.0 telescope long time ago, but to get acceptable results, all the mirrors had to be aligned to something like 0.5mm!!!). great if you have the time AND you bought a collimator with the telescope.

The F-ratio of a telescope is NOT like the F-stop of a camera. The focal ratio of the telescope is the focal length divided by the diameter of the mirror, i.e. a 200mm mirror (8") with an 800mm focal length will give you a F4.0 telescope
edit on 14/10/2011 by Hellhound604 because: added the last part


This is good to know because I was actuallu looking at the F4.0`s..thanks.



reply posted on 15-10-2011 @ 09:30 AM by Hellhound604
reply to post by lbndhr


Yes, that was a trap I fell into when I bought my first real telescope. The F4.0 Newtonian was quite a lot cheaper than the F5.0, and more practical to transport, but collimating the mirrors was a b*tch. I had to recollimate everytime I took my telescope somewhere else, and in the end that telescope ended up in the attic. Also, coma's are quite severe on a fast telescope like that.


reply posted on 15-10-2011 @ 08:03 PM by lbndhr
Originally posted by Hellhound604
reply to post by lbndhr


Yes, that was a trap I fell into when I bought my first real telescope. The F4.0 Newtonian was quite a lot cheaper than the F5.0, and more practical to transport, but collimating the mirrors was a b*tch. I had to recollimate everytime I took my telescope somewhere else, and in the end that telescope ended up in the attic. Also, coma's are quite severe on a fast telescope like that.


What is a coma?


reply posted on 16-10-2011 @ 03:50 PM by Hellhound604
reply to post by lbndhr


only stars close to the optical axis appear as pinpoint images, the further from the optical center the stars are, the more spread out they appear.

www.opticalmechanics.com...
www.skyandtelescope.com...


reply posted on 16-10-2011 @ 04:08 PM by lbndhr
reply to post by Hellhound604


ok, then this telescope I'm highly considering has that cp.a fix on it. It is the Celestron ETX-80AT Astro telescope with autostar controller, any opinion on this one as a first telescope?


reply posted on 16-10-2011 @ 04:23 PM by Hellhound604
Originally posted by lbndhr
reply to post by Hellhound604


ok, then this telescope I'm highly considering has that cp.a fix on it. It is the Celestron ETX-80AT Astro telescope with autostar controller, any opinion on this one as a first telescope?


I guess you mean the Meade ETX-80AT. It will give you very good planetary views (better than a reflector), but does not quite have the light-gathering of a large reflector. Also, because it has an alt-az mount, the field will rotate as it tracks the stars, so you can't use it for very long exposures, but don't despair, you can still take lots of short-exposures, and then use some software like Registax or Aip4Win to de-rotate the stack ..... but it is a very nice telescope, from what I have heard

You will see, if the bug bites you, you will end up with at least 2 scopes, a small portable one, and a large light-bucket that is NOT portable, lol .... good luck. It is a great hobby
edit on 16/10/2011 by Hellhound604 because: (no reason given)



reply posted on 16-10-2011 @ 04:51 PM by lbndhr
reply to post by Hellhound604


your right its the Meade, it also comes with the moon filter, and has an added feature I switch it to a nature scope, I will go back and look at the specs I think it has ability to be used manually, tea king off setting, but ya I'm ordering it and will be using it by weeks end, and as for a second,yep already researching the next level for mid next year. Thanks for the time on advising me,this isn't a fast puck decision, I want best I can get for reasonable price to being me into space. Peace


reply posted on 18-10-2011 @ 07:07 AM by lbndhr
reply to post by shasa


If only I had that much $$$$. for knwo I will go with the 10in a bit smaller but good enough to get me understanding the skies, and save for the real deal, big girl telescope. for the future enthusiast, AMazon.com will bring the best deal on a New purchase, what I ordered was $489.00 plus taxes and shipping fees, from Meade, from Amazon same exact telescope $269.00 out the door into shipping. those $8000.00 telescopes are going for as low as $2000.00 know this is what im talken about peace


reply posted on 18-10-2011 @ 11:46 AM by Hellhound604
Originally posted by lbndhr
reply to post by shasa


If only I had that much $$$$. for knwo I will go with the 10in a bit smaller but good enough to get me understanding the skies, and save for the real deal, big girl telescope. for the future enthusiast, AMazon.com will bring the best deal on a New purchase, what I ordered was $489.00 plus taxes and shipping fees, from Meade, from Amazon same exact telescope $269.00 out the door into shipping. those $8000.00 telescopes are going for as low as $2000.00 know this is what im talken about peace


but if you have a large light-bucket you cant throw it on your back and take it along when you go hiking.....



reply posted on 18-10-2011 @ 05:51 PM by lbndhr
reply to post by Hellhound604


if or when I would consider a large scope it would stay at home, I live way out in the middle of nowhere no mountains pure open dark night skies. Its perfect for sky viewing.
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