First night out, and EP question

[rathalian]

First night out tonight with my 10" Dob. After spending about 30 minutes figuring out how to find Saturn I lined the the laser spotter > finder scope > main scope up with our distant neighbour and....WOW!

Looks like my collimation worked a treat as I got to see a clear, bright and in focus Saturn with a good view of the rings and the shadows on the planet. There is something very humbling seeing something with your own eyes for the first time

4 GSO Super Plossls came with the telescope - part of why I'm opening this thread. This is what I've found with them so far (based on an F5 / 1250mm tube):

25mm - good for general viewing, although not enough magnification for Saturn; I could see the rings but not much else. Good eye relief and FOV and lots of glass at the exit pupil.

15mm - not much better than above re zoom, less FOV OK eye relief, decent exit pupil.

9 mm - seemed to be the sweet spot out the the lot re FOV vs. eye relief vs. zoom. Saturn was quite defined, with shadows and some colour. Small exit pupil but useable.

6 mm - almost unusable re continual adjustments of the scope. FOV was maybe 10 seconds worth (with the edges going out of focus) and the eye relief was terrible i.e. really hard to use. Really small exit pupil.

I assume I'm using eye relief correctly here ? i.e. the distance my eye has to be from the Plossl to see an image properly.

I'm wanting to get a bit more zoom than the 9mm can deliver as there is buckets of lights and the image is sharp, however want to be able to view comfortably and for more than 10 or so second before adjusting.

What are some options without spending the big bucks? I've read in another thread it might be worth getting a 2 x Barlow to squeeze a bit more out of the lenses I have; or is it worth looking at an alternative?

[big_dav_2001 (Davin)]

Hi there

Sounds like your after some smaller focal length EP's ( ie: more zoom) with a larger FOV (ie: less chasing objects). I'm not sure what the FOV is on the GSO plossls, but ive got the same EPs for my 12" GSO dob, and I upgraded pretty quick too. But since upgrading to the the Baaders I've got now (see below), I've found that I hardly ever use anything above an 8mm, and even that only comes out on nights of almost perfect seeing. At high mags, any poor seeing is also magnified by the EP, and it's very easy for your eyepieces to push your telescope beyond it's capabilities and degrade what your seeing.

My advice would be to get used to looking at lower magnifications for a longer time as it passes through the FOV rather than go for high magnification views for a few seconds at a time. You'd be surprised at the subtle details your eye can pick up even at lower magnifications if it's given enough time to see them.

That said, there are some good mid-range EP's out there with good FOV's, Orion Stratus and Baader Hyperion are the two that come immediately to mind, and depending on your budget, you could always aim for some Televue Ethos', though they're pretty pricey.

Davin

[Liz]

Hi Rathalian ... i have a 10" Dob, and for a higher mag I love my Explore Scientific 4.7mm EP/82dg. Cant remember what it cost bit wasnt a fortune. I recently bought a 5mm Televue Radian which I dont like (has good reviews) ... for sale if you want it.

[mental4astro (Alexander)]

Hi Rathalian,

Plossl eyepieces used to be the bees-knees of eyepieces close to thirty years ago. The lens design is still very good, giving plenty of eye relief (how close you need to park your eye to see comfortably into the eyepiece and still see the whole FOV). However, this performance drops of very quickly with the really short focal length EPs. You've noticed this already with the poor 6mm you have. The 25mm you've found to be a comfortable low power EP.

In the last 30 years, eyepiece design has come a long way. Improvements in glass technology has provided for incredible designs that give fantastic wide FOVs, and extraordinarly long eye relief. Best thing though, many of these new eyepieces are also inexpensive.

I'd suggest you look at the two eyepieces here fellow IIS member Sylvain is offering us here on IIS. These 6mm & 9mm TMBs are truely marvelous. I've got both, having bought the 6mm one year before Sylvain's offer, and at what I thought was a bargain price of $110 THEN! Now, you can get both for that.

The eye relief these EPs have is fantastic. They are as easy to use as your 25mm plossl, and have a FOV of 60 degrees. While there are wider FOV eyepieces out there, 60 degrees still offers plenty of 'drift time' through the EP, meaning less shifting of the scope. The quality of the image across the whole field is brilliant too. The quality of the image is fantastic too: the coatings are first rate.

Another thing is that they are also light weight too.

All of this is to say that you don't need to spend big bucks to get good gear.

[Gem (Grant)]

Your experiences are expected. The higher you push in terms of mag, the harder seeing will be regardless of the EP. On good nights you might push it up beyond a 9mm, but not on a regular basis.
I found the longer I was observing with my 10" dob, the less I looked at planets. So I would advise caution before jumping out and spending your budget on a top eyepiece that is less than 9mm in focal length. I went through the same as you and got a 4.8mm Nagler when I first got my dob. I was so excited to see the moon and planets that I wanted a large FOV (same as you) to not move the scope all the time and higher mag... I wish I hadn't none since i went on to enjoy globular clusters much more than the planets (but maybe that is just me!).
I was only 20 or so when I got that Nagler, so it broke my budget for a while. I was careful in making my next purchase and got a 32mm TV Plossl - best decision. Good quality. Low power suited what I ended up viewing (deep sky). Good price.

Food for thought!

[Gem (Grant)]

I see you are probably from the ACT too... so if you want to try an eyepiece one night - let me know!

I have (of varying qualities):
4.8mm Nagler
12.5mm Celestron plossl
15mm Celestron Axiom (82 degree FOV)
25mm Sirius Plossl
25mm Celestron Plossl
32mm TV Plossl
40mm Bintel plossl

The ones in bold get the most use.

[ZeroID (Brent)]

Hi Rathalian and. You've made some good observations about your experiences so far. Alex is on the ball here. I just bought both the 6mm and 9mm from Sylvain and they are heaps better to use than the old Plossls and a good bang for the buck option.
Don't kock the bigger EPs, 25 15 etc. Saturn is only one target and the DSO's need totally different EPs from planetary targets.
My current EP range is down in my Sig and I am still refining and upgrading them. It takes time to learn how to use them and what they are best for and also to train your eyes to 'see' better.

Good luck and have fun learning. Plenty of good advice and help on here so hang around.

[rathalian]

Thaks all for your responses.

I am indeed from around Canberra (Greenleigh to be specific).

We're pretty lucky here as we live in the hills up behind Canberra, with a large deck surrounded by cleared space, then bush, so the night skies are pretty dark facing away from Canberra (trees protect the skyline on the Canberra side)

After posting earlier I purchased a couple of new eyepieces. A 6mm TMB off Sylvain (seemed like a good buy) and a Televue 11mm Plossl for around $60 delivered (looks new) - both forum purchases that I couldn't be happier with.

Unfortunately it's either been heliishly cold or cloudy so I've not tried them but it was clear that the TMB eyepiece was in a different league vs. it's GSO brother.

When / where do the local Astro guys catch up ? Oh and if you'd like to come over with your porta-scope and set-up out the back with me (and let some experience rub off) we brew a mean hot chocolate

[Brian W (Brian)]

Just something to think about. You have a fine scope that will do visual observing really well.

Eye pieces and accessories will turn it into a great planetary or a great faint fuzzy or a great nebula scope.

Before you start emptying your wallet you could take some time and figure out what really turns your crank and just where you can put the money for the most satisfaction.

Brian

[Gem (Grant)]

Originally Posted by rathalian

When / where do the local Astro guys catch up ? Oh and if you'd like to come over with your porta-scope and set-up out the back with me (and let some experience rub off) we brew a mean hot chocolate

Let the skies clear and give us a call... my scope is portable . Logan's isn't. Otherwise, there is the Canberra Astro Society members too.
The forecast for this weeks doesn't look good though...