MnAstro Forums

I have an 8" SCT, F10, FL 2000 mm scope. I would like up purchase better eyepieces. I came across this site: https://www.bhphotovideo.com/c/product/ ... 25_mm.html and am interested in the 25, 18, 12 and 9 mm eyepieces. All have a 60 degree AFOV and 16 mm eye relief. At the bottom on the page is a 2X Barlow. I am wondering if purchasing the Barlow would be a better deal and I can reduce the eye pieces to the 25 mm and 18 mm. I have never used a Barlow before and reviews of a Barlow really don't convince me they are a good deal. I am also interested in the OIII filter, also at the bottom of the page. I am a visual observer only. The total cost for the above items is around $500, four eyepieces and filter. Any input will be greatly appreciated.

My personal experience is that 90 percent of the time I use one eyepiece. There may be a time when sky conditions allow higher magnifications. Barlows are billed as a way to double the eyepiece magnification for the eyepieces you have, but personally I would rather just get the eyepiece with he magnification your looking for.

My experience also may be a familiar one to many others... You want to get a better eyepiece than those that are included with the telescope, but you don't want to spend to much, so you end up getting a series of eyepieces that cost $100 - $150 or so. Now these are better than what you started with, but if you get a view with a high end, wide field eyepiece you'll realize you now have a bunch of mid-range eyepieces you'll never use again.

Hindsight being what it is and if I had it to do over, I would save the intermediate eyepiece purchase and get the high end eyepieces we all seem to end up with.

Of course I don't know what your exact situation is, but I would reccomend this as a process:
Bring your scope to one of our sites to view through the high end eyepieces we have. ELO, CGO, even LLCC would have a number of eyepieces to try before buying anything. We'd also have a variety of filters to try as well.

Now I didn't get into the magnification / field of view (FOV) debate and what the "best" eyepiece for your scope is, but... The scopes at ELO for the most part have default eyepieces that have around 100x and about 1/2 degree FOV (41 mm eyepiece). This is what we observe at 90 percent of the time. Occasionally, if conditions allow, we may go as far as doubling that with a 20 mm eyepiece. Generally speaking, for your 8" SCT, a 20-25mm would fit this range to start and a 10-12mm for doubling that.

I'll get off my soapbox and let others chime in, but please feel free to try the eyepieces we have to help you decide what's best for you and hopefully avoid the expense of the mistakes the rest of us have made.


Merle

I will generally agree with what Merle said. I would also like to add that I have the same size/type SCT telescope, and really appreciate having a 40 mm Plossle (spelling?) which will show me either the entire sun or moon with a little bit of margin around it. This is ideal for eclipses, transits, sunspots and a nice all-moon view.
It is also nice for other wide area objects and views of open clusters. The images tend to be brighter at lower magnification.

Here's a forum topic where eyepiece selection advice had been covered before.

viewtopic.php?f=6&t=7459&p=36766&hilit=televue#p36766

I'll also mention that most of us use 2" diagonal and eyepieces to maximize the view of the sky. A little research and testing goes a long way. Remember, telescopes may come and go, but the eyepieces you get can be with you forever.


Merle

Matt, you should compare your 40mm Plössl with a 32mm Plössl. The 1.25" barrel prevents the field stop / field of view from being any larger in a 40mm compared to a 32mm. So you'd get more magnification at the same field of view in the 32mm Plössl. The image circle will appear larger.

To counter some of what has already been said. An f/10 telescope is going to be less demanding on eyepieces than faster telescopes. The angles of light at the image plane are less severe, and the depth of focus at f/10 is greater than the depth of focus on faster telescopes. This means there are many, less expensive, eyepieces designed to work in your SCT that will not be as great in faster telescopes. Of course... if you catch aperture fever, you'll have many different scopes anyway...

Shop around for prices. For instance: https://www.astronomics.com/eyepieces-b ... series=490 are currently cheaper than your link. Also check if they are in stock. Can't say much about the x-cels having not used them.

I thank all of you for your input and information. I sure wish I could see into the future and find out if I get aperture fever. I went from a bicycle to a Cadillac with this telescope. It is the one that David Schultz gave away in his Telescope Garage Sale. I am still stunned he did this for MAS and I was the lucky one to get this scope. I am in the process of purchasing accessories such as a tote to carry the scope, dew shield, AC/DC power supply etc. My current eyepieces don't do this scope justice. I borrowed a MAS loaner scope just prior to David's sale and am using the MAS eyepieces on my new scope.

So, Clayton...
At a past b-sig event, you showed me a really nice eyepiece on my c8 that you called the "pineapple". What were the specs & cost for that? I think it was it was a 26mm or maybe a 32mm, and it was really nice and a wider angle than my 40mm.
That eyepiece would probably qualify for the category that Merle was describing as the future eyepiece you should save your money for, and I might just do that myself someday.

matt_2018 wrote: ↑Tue Jun 08, 2021 12:59 pm Clayton...you showed me a really nice eyepiece...called the "pineapple"...I think it was it was a 26mm or maybe a 32mm.

Before Clayton chimes in, here's my guess:

(It's on my Christmas wish list.)

Merle, you described exactly the thought process I've been going through this week and I was getting close to buying some eyepieces for ~$100. I'm going to put that on hold and wait until I have the chance to bring my scope to ELO and try out some nicer pieces.

I eventually found that 90+ % of my viewing was done with just two eyepieces that yielded 44X and 127X magnification (an Orion 2” Q70 and a Nagler 1.25” respectively). Using a barlow lens for the remaining few % is not too onerous.

I echo Merle’s advice to consider paying the blackmail up front for a few top of the line eyepieces rather than buying a bunch of cheap eyepieces before eventually breaking down and paying the blackmail anyway. In the long run cheap optics are not a bargain. (Although at $666 I would balk at buying that 31 mm Nagler.) This would also extend to barlow lenses. When you borrow eyepieces at star parties you might also run a comparison of achromatic and apochromatic barlows to see if you think the apochromatic is worth the extra cost.

With a focal length of 2000 mm I would imagine you would want wider field of view than what 60° AFOV would yield, especially if you commonly view wider targets such as open clusters (e.g. M44 FOV=1.2°). In addition to the magnification, I recommend crunching the FOV for any eyepieces you consider. Unfortunately, AFOV’s > 60° cost significantly more.

Regarding barlows, in addition to increasing the magnification (and decreasing the actual field of view) Barlow lenses also have some other effects. The book Telescope Optics by Rutten & van Venrooij (page 155) mentions that:
1. a barlow can decrease the amount of coma (edge distortion) of an eyepiece.
2. when used in fast telescopes (i.e. low f ratio - such as a f 5 Newtonian) a barlow can sometimes allow the use of a longer focal length eyepiece with correspondingly longer eye relief (the distance between the eyepiece and the eyeball). This can be especially useful for people who wear glasses, since the distance between the eyeball and the glasses is a major fraction of the eye relief distance.

^ Conversely to the above, a Barlow also increases the eye relief on long eye relief eyepieces, which can actually make it difficult to place your eye without blackouts. Tele Vue corrects this with their Powermate “barlows”.

One piece of advice I would give is to have an eyepiece that gives you the largest true field possible in your scope. You might not use this eyepiece the most, but you will love it for finding objects.

Before Clayton chimes in, here's my guess:

Close Mr. Cooper. If I remember correctly it was a Discontinued Meade 5000 SWA 40mm 68° AFOV. The SWA was a Wannabe 41 Panoptic. However it was not quite as good. For the price I paid used it's in my eyepiece case until a 41 Pan comes my way. Its far from a 31mm Nagler 82° AFOV. I think Matt was using a 40mm Meade 4000 super Plossl at 44° AFOV much less TFOV than either.

I would take the 31mm Nagler if given a choice.
photo from web
photo from web

If I recall correctly, the nickname for the 31 Nagler was: The Grenade!

clayton wrote: ↑Thu Jun 10, 2021 1:48 pm Happy he made this before he turned to imaging.

Observing and imaging are two sides of the same coin. I'm glad my eyepiece calculator/chart is getting use.

Observing and imaging are two sides of the same coin. I'm glad my eyepiece calculator/chart is getting use.

FYI, Kris's calculator link is on the Equipment, Gadgets... forum HERE

Kurt, I think a grenade basically looks like a metal pineapple, so these are both very good descriptions!
I think it would hurt to get hit by either of those eyepieces.
Matt