# Planning to buy a first telescope?

by turbo
Tags: planning, telescope
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 Quote by AnTiFreeze3 For a beginning telescope, how does this look? http://www.telescope.com/Shop-by-Bra...tValueIds=4519
That one is alright, but I'd recommend a dobsonian to start off with. Its MUCH easier to setup and use. It is quite literally, take outside, set telescope on mount, and observe.

 At least where I'm looking, I don't seem to be finding anything like what you're describing. Would you mind linking me somewhere?
http://www.telescope.com/Telescopes/...CategoryId=398
 PF Patron P: 7,345 Good advice, Drakkith. Increased aperture and a parabolic (vs spherical) primary mirror,and a smooth dobsonian mount are all good things in a first scope. The mount featured in the first example is so flimsy as to be worthless. Many nights of frustration are in store for newbies that purchase scopes such as those. I hate to see people wasting money like that, because such sub-standard gear ruins their interest in observing. That is not good for any of us.
 PF Patron Sci Advisor P: 8,889 Another option http://www.adorama.com/CNAM130EQMD.html. It's slightly smaller [130mm vs 150mm primary], less expensive [$210 with free shipping], and is equatorial mounted [CG3]. The good: The optics are very good and at f5 will deliver a noticeably brighter and wider field of view. The equatorial mount makes it easier to find and maintain objects of interest in the field of view. The bad: The eyepieces and finder are toy-like. The tripod is less than stellar, but, mostly adequate. You will need new eyepieces[e.g, Knight Owl 20mm superwide ~$35]. The wide field of the primary makes replacing the finder scope less of an issue.
 PF Patron P: 10,406 Note that the brighter views are solely the result of less magnification with the same eyepiece since the f5 scope has a shorter focal length, and magnification is the focal length of the scope divided by the focal length of the eyepiece.
 P: 243 Thanks for the advice, everyone! I'm probably going to go with the Dobsonian that Drakkith linked me to, and I actually found some package that they're offering that includes that telescope with a Barlow 2x eyepiece for only $10 more. Chronos, were I spending my own money, I would probably go with the one you mentioned, but I enjoy the benefit of having religious parents who take Christmas seriously ;)  P: 243 So I got the 6" dobsonian that's up in the link that Drakkith posted. I got some deal with an included Orion 2x Shorty Barlow lense, along with some "beginners accessories," but I was mainly looking for the 2x Barlow. The telescope comes with a 25mm eyepiece, and that's it. So with the Barlow, I essentially have a 25mm eyepiece, and a 12.5mm eyepiece. I'm wondering which other eyepieces would be worth investing in. I've heard that eyepieces that provide a wider view (30+mm) are beneficial, but I also see myself wanting some better viewing for planets and the moon, so something under 10mm would be nice as well. Which magnification would work best for the telescope that I'm using (this one)?  PF Patron Sci Advisor P: 8,889 I agree that is a nice dob, have fun with it! I stand firm that you need a good [and ideally inexpensive] wide field EP.  P: 243 How's this look? I need to be a little cautious, now that I'm spending my own money.  PF Patron P: 10,406 I bought a pack of plossl eyepieces that came with a 32mm, 16mm, 9mm, 6mm, 2x barlow, and some filters. Now, I am by no means an expert visual observer, so I really couldn't tell you if they are "nice" or not, but I enjoy them. I think the whole pack was around 80 dollars. I think it was well worth the cost and I actually use almost every eyepiece regularly. The 6mm is about the only one that isn't used that much, but only because I'm well past my scopes resolution with it. But my scope is also F/8, so a shorter f-ratio scope may get more use out of it. I'd consider something like this before shelling out 60-100 dollars or more PER eyepiece, at least until you get a bigger scope. I can almost guarantee that you will enjoy them. Save the multi-hundred dollar eyepieces for when you are more experienced and can afford them. BUT that's just my opinion. Others here who have more visual experience may tell you to stick with the quality eyepieces. Edit: Here's a link to a kit similar to what I bought. http://www.telescope.com/Accessories.../47/p/8890.uts I must have gotten a packaged deal or something, as this pack is 150 dollars, almost twice as expensive as mine was. Although it does come with 5 eyepieces instead of the 4 mine came with. And I'm sure that 40 mm eyepiece isn't cheap. That's a lot of glass compared with my 32mm, the largest in my kit. You may get some use out of the filters. They are fun to play around with and can show you some details you may not be able to see without them, but they are by no means necessary. The moon filter can be a nice thing too, as the Moon is VERY bright and usually hurts my eyes a bit unless I use one. (And it ruins your night vision if you view the Moon when it's close to being full) All in all I'd recommend something like this just to have many different options. I'm sure the quality isn't amazing, but I've been using my kit for upwards of two years now and I have zero problems with them. Also, plossl eyepieces aren't generally "widefield" by most observers standards, so if you take Chronos's advice and decide on a wide field eyepiece you will probably need another type. Here's a list of common eyepiece types: http://en.wikipedia.org/wiki/Eyepiece#Eyepiece_designs The Nagler is a popular wide-field design, but it is VERY expensive.  PF Patron Sci Advisor P: 8,889 The ideal wide field would be around 30mm with at least a 68 degree apparent field of view. Unfortunately, ep's of this description are pricey and the choices are pretty limited in the 1.25" size. I would check out ebay, sometimes you can snag one on the cheap. Just make sure it has a 1-1/4 barrel and not 2".  PF Patron HW Helper Sci Advisor P: 3,720 The first thing I would get is this variable polarizer filter. I don't know of any 30mm 68 degree eyepieces in the 1.25" form factor. The only ones I'm familiar with in the 1.25" barrel size are the 24mm ones like the Explore Scientific and the now discontinued Meade Series 5000 SWA 24mm which you can still pick up used for$90-$100. I think you should pick up a nice 3X Barlow and keep using the 25mm plossl. A 3X barlow will give you ~150X which is pretty good magnification for that telescope. P: 243  Quote by chemisttree The first thing I would get is this variable polarizer filter. I don't know of any 30mm 68 degree eyepieces in the 1.25" form factor. The only ones I'm familiar with in the 1.25" barrel size are the 24mm ones like the Explore Scientific and the now discontinued Meade Series 5000 SWA 24mm which you can still pick up used for$90-$100. I think you should pick up a nice 3X Barlow and keep using the 25mm plossl. A 3X barlow will give you ~150X which is pretty good magnification for that telescope. There are actually a decent amount of 30+mm eyepieces for 1.25", however hardly any of them have a FOV of 68 degrees, and the few that do have it don't go much higher than that without getting incredibly expensive. (This is just what I've seen after browsing around on the internet for a while). The telescope that I have coming in already has a 2x Barlow, so I'm wondering if a 3x Barlow would be a little overkill. With the 25mm Plossl I'll have 48x magnification, and with the 2x Barlow + the 25mm, I'll have 96x magnification, whereas with the 3x Barlow it would be 144x. Is that significant enough to be a worthwhile investment? I'm thinking that a more powerful eyepiece would be more beneficial, if I'm just trying to zoom in farther. As for the filter, that looks like a good investment.  PF Patron P: 10,406 Magnification isn't as big of an issue as one might think. Your resolution on planets will be limited by your scopes diameter and for most deep sky objects less magnification may be better than more, as you concentrate the light and make them easier to see.  PF Patron Sci Advisor P: 8,889 Orion stratus also has a 24 mm wide field, but, it runs about$150. Konig has a 20 mm for about $60 and Knight Owl has one for$34, but, 20 mm is not terrible. With a 68 degree FOV you should have a true field of view a little over 1 degree and 60x magnification, which is about where you want to be. A 3x barlow would be a waste of money, IMO. You will rarely have nights where you can effectively use more than 25-30x your aperature in magnfication. An inexpensive 6 or 8mm super plossl or ortho will be enough for those rare occassions.
 P: 243 Thanks for the help, everyone. I'm sure that I would've made at least one stupid purchase had I not checked here first. I'll pick up the Knight Owl 20mm along with that variable polarizer filter. Although, if I were to be using the 20mm with the wide FOV, and then slap on my 2x Barlow, that wouldn't affect the FOV at all, would it? I'm thinking not, but want to make sure it doesn't because I would like to get up to 10mm with a nice, wide FOV. EDIT: I also found a \$15 new Super Plossl 10mm EP on ebay, but I'm hesitant to do anything because my 2x Barlow would essentially turn my 20mm Night Owl into a 10mm as well. Is the quality of a view between an actual eyepiece, and an improved-through-using-a-barlow EP significantly different? EDIT #2: So I figured out that using the Barlow on the 20mm Night Owl with a 68 degree FOV will decrease its FOV. My new question is how that decreased FOV would compare to a 52 degree FOV of a Meade Super Plossl 10mm, seeing as how I'm not sure how to do the math behind this.
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 Quote by AnTiFreeze3 There are actually a decent amount of 30+mm eyepieces for 1.25", however hardly any of them have a FOV of 68 degrees, and the few that do have it don't go much higher than that without getting incredibly expensive. (This is just what I've seen after browsing around on the internet for a while).
I don't know of any that are 30mm and have a 68 degree or larger AFOV that come in a 1.25" barrel. If you've seen one, I'd be interested to hear about it.

 The telescope that I have coming in already has a 2x Barlow, so I'm wondering if a 3x Barlow would be a little overkill. With the 25mm Plossl I'll have 48x magnification, and with the 2x Barlow + the 25mm, I'll have 96x magnification, whereas with the 3x Barlow it would be 144x. Is that significant enough to be a worthwhile investment? I'm thinking that a more powerful eyepiece would be more beneficial, if I'm just trying to zoom in farther. As for the filter, that looks like a good investment.
I think you'll find that 144X with a plossl + barlow is the same as 144X with an 8-ish mm EP. There is no overkill at 144X. What WILL be different is the eye relief. Plossls give you an eye relief about .7 times the focal length of the EP so an 8mm plossl will have about 5-6 mm... pretty tight, IMO. The 25mm EP will still have a luxurious 17 to 20mm eye relief. It will be much more comfortable to view through. 144X represents about 25X per inch of apeture which is well within the magnification range of your telescope. I view at around 150X all the time and find that most nights will support it where I am, west of San Antonio.

If you don't want to invest much, you might consider an inexpensive extension to get your 2X barlow up to about 3X. A barlow lens is like a projector lens in that the farther away you place your eyepiece, the larger the magnification. This would definitely not be overkill and would represent a significant increase in magnification vs. the 2X barlow + 25mm (96X).
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 Quote by AnTiFreeze3 Although, if I were to be using the 20mm with the wide FOV, and then slap on my 2x Barlow, that wouldn't affect the FOV at all, would it? I'm thinking not, but want to make sure it doesn't because I would like to get up to 10mm with a nice, wide FOV.
The apparent field of view- the angular size of the view you see at the eyepiece- will remain the same. The true field of view- the angular size of the part of the sky being viewed- will decrease. If you double the magnification, you halve the TFOV.

 So I figured out that using the Barlow on the 20mm Night Owl with a 68 degree FOV will decrease its FOV. My new question is how that decreased FOV would compare to a 52 degree FOV of a Meade Super Plossl 10mm, seeing as how I'm not sure how to do the math behind this.
The 68 degree FOV mentioned here is the apparent field of view and will not change. Anytime you increase the magnification, however, the true FOV will decrease.

http://www.telescope.com/Articles/Cu...94/p/99822.uts

http://en.wikipedia.org/wiki/Eyepiece#Field_of_view
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 Quote by AnTiFreeze3 EDIT #2: So I figured out that using the Barlow on the 20mm Night Owl with a 68 degree FOV will decrease its FOV. My new question is how that decreased FOV would compare to a 52 degree FOV of a Meade Super Plossl 10mm, seeing as how I'm not sure how to do the math behind this.
I don't think so. I think you are confusing actual FOV with apparent FOV. Apparent FOV remains unchanged but whenever you magnifiy the image you lose actual FOV. You will be looking at a slightly smaller piece of the sky (actual FOV) but the apparent FOV will remain at 68 degrees. Some report that the barlow can vignette the view a bit but it shouldn't be that noticeable.

edit: Jimmy beat me to it.

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