Planning to buy a first telescope?

Chronos

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".

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.

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).

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.

Drakkith

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.

Chronos

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.

AnTiFreeze3

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.

chemisttree

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.

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).

Jimmy

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.

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

chemisttree

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.

AnTiFreeze3

As for the 32mm with 68 degree AFOV or larger, I was mistaken... I don't know of any. If there are any, I'm assuming that they would be incredibly expensive.

That extension piece actually seems interesting. It doesn't explicitly state that it increases the the magnification of a Barlow lens, but if they work as you claim they do, then I would be all for it.

"The power of an adjustable Barlow lens is changed by adding an extension tube between the Barlow and the eyepiece to increase the magnification." - Wikipedia.

They do mention an "adjustable" Barlow lens, but would a regular, Shorty Barlow 2x lens be acceptable as well?

And from what I've gathered, if I were to increase the distance between the eyepiece and the Barlow lens by the length of the Barlow lens one time, then I would bump up its magnification from 2x to 3x. If I were to increase the distance by the length of the Barlow lens again, it would go from 3x to 4x.

So the Shorty Barlow 2x lens is 3" long, whereas the eyepiece extension tube can increase the distance between the EP and the Barlow by 2", so I should be increasing the magnification of my Barlow from 2x to ~2.67x magnification. That would give me potentially 160x magnification with my 20mm lens (with my scope having a 1200mm focal length), which is, I think, as much as I'll be getting out of my scope, aside from any crystal clear viewing conditions.

That actually seems like the perfect solution, thanks for the idea!

EDIT:

About the corrections, thanks for clearing that up. I think I was a little confused about the difference between the AFOV and FOV. I should've known that zooming in on something obviously doesn't allow me to see as much of it....

AnTiFreeze3

So I'm done with all of my purchases now.

In the instance that someone else seems to be in a situation similar to mine, with a budget similar to mine, with interests similar to mine, I'll list what I've purchased, from where, and how much the total cost was for it all:

- This telescope (Costs $349.99, but note that I was able to snag a Cyber Monday deal and ultimately got it for $299.99).
- This 20mm eyepiece (costs $33.95).
- This Variable Density Eyepiece Moon Filter Set (was $19.95 at the time; you'll have to scroll down a bit to see it).
- This eyepiece extension tube (costs $19.99).

The telescope also included a 2x shorty barlow, so take that into account with it all as well.

The total price comes out to $373.88 (with the deals that were present at my time of purchase).

Considering the fact that I'm getting the telescope and the accessories that come with it for Christmas, I spent well under $100 of my own money, got some very nice equipment, and am very pleased with my purchases. Once again, thanks for all the help that everyone has provided me; I probably won't need to stop by here again until it's time to unwrap presents

Chronos

AFOV is the apparent field of view. When you increase magnification, your AFOV is unchanged, but, true field of view [TFOV] decreases commensurately. Your choices look reasonable. The extension tube is probably a waste of money, but, I've wasted a lot more money than that on dubious purchases.

chemisttree

Believe me, the extension tube works as described with the shorty barlow. I've been using mine now for 6 years and it works fine. Eye relief at short focal length is very tight but use a longer FL EP with a barlow and it's nice and comfortable. You can take your time and really concentrate on what you see. You will note that a barlow is built in to every Nagler eyepiece ever made for just that reason.

Use the variable polarizer filter on the end of the barlow, equip it with the extension tube and view comfortably through the 20 or 25 mm EP on the Moon. I can't imagine a better way to spend an evening in the back yard.

turbo

Some good advice here. I have some very short FL eyepieces and eye-relief can be tight. I found out that I have "just" enough astigmatism to make observing fine detail problematic, so using a Barlow and a longer EP works out well, since I can leave my eyeglasses on. That short Nagler stays in the case most of the time. A longer EP with a Barlow is more comfortable to use.

AnTiFreeze3

So after a quick google search, I found a pretty legitimate, professional, and interesting local astronomy club. There's a membership fee ($20), but they have their own observatory with a 20" telescope, with its own location in a park.

Most of the members seem to be older guys, but I'm still applying. It should be fun.

AnTiFreeze3

How useful are collimation eyepieces? I wouldn't shell out the money for a laser collimator, but some of the eyepieces (like this one) are as cheap as $30, and appear to work very well.

My scope came with a collimation cap, but even after trying to collimate my telescope, I'm still not sure if it's properly collimated.

Drakkith

Welcome to my world. My Newt is...terrible. Flimsy design REALLY brings it down. My collimation on it falls apart just by slewing from one part of the sky to another. Couple that with the fact that I am TERRIBLE at collimation. I found the laser collimator to be the most useful for me, while the collimator eyepiece was decent also.