Second night with new Dob 8" - would like some new eyepieces

[aventic]

Hello folks.

Had my second observation session last night. I watched Jupiter and its 4 moons for quite a while, and amazing it sure was!!

The eyepieces I currently own is a 10mm and a 25mm that came with the telescope. After what I saw last night, I want to get in just a little bit closer on object such as Jupiter, so thinking maybe a 5 - 6mm eyepiece will suffice.

What do I look for?

• Field of view
• Eye relief
• Coating, multiple or fully multicoated etc
• Anything else?

Personally I've been looking at these two:

• Omegon Cronus 6mm: http://www.astroshop.eu/omegon-cronus-wa-6-mm-1-25-/p,32982
• Celestron X-Cel 5mm: http://www.astroshop.eu/celestron-x-cel-lx-1-25-5mm-eyepiece/p,21918

There is a big nod in price, will the expensive one be that superior to the cheap one? And if it matters I'm all in for observation no AP

Thanks in regards!

[Qualia]

I've found my most used EPs for general DSO viewing (not open clusters) have always been around that 120x mark and then backing off from that with something around 90x. The former will give you exit pupil of around 2mm and the latter around 2.8mm. If you get a 25mm , you'll have a nice finder EP and one useful for open clusters and if you got yourself a decent Barlow with just these 3 EPs you'd have a nice spread like this:

25mm / 12.5mm = 48x, 96x.
14mm / 7mm = 85x, 170x.
10mm / 5mm = 120x / 240x.

In my 10" f5, for example, I use a 24mm Panoptic, 14mm & 10mm Delos. The lower mags are useful for general hunting and framing largish objects, the middle ground for globs, galaxies, nebulae, the more limited higher range for Saturn, Jupiter and Lunar work and the 240x for those exceptional nights with Saturn or the Moon. If you got yourself some Baader solar filter, your 48x would also be fine for white light sun observations.

When it comes to planetary viewing, I've noticed that slight changes in the focal length of eyepieces makes quite a difference to what can be tweaked from the given object. In terms of general useful magnification, you might find the following parameters useful:

For Jupiter, I typically use mags between 125x to just over 200x. The mean power seems to be around 160x to 170x.

For Saturn, I have found 140x to over 200x useful mags to play around with. You can go higher here, but a lot will depend on the night's atmospheric conditions.

For Mars, around 250x when it is in a good position (you're going to have to wait another year for that) which still means seeing conditions will have to be very good. As such, Mars isn't a particularly forgiving planet.

When it comes to eyepieces, a lot will depend on budget. For planetary work, I use Orthos and in particular those that were made by Baader - the Baader G.Os which are no longer in production but regularly crop up on the secondhand market from anything between £50 to £100. The quality of image in these EPs is probably almost as good as it gets. Hutech's are said to be identical in quality and by fortune FLO are selling them. If you want a similar quality image EP but with a wider field of view and perhaps a more comforting eye-relief, you're going to have to spend a far bit more and perhaps ultimately delve into something like a Pentax or Tele Vue.

Yet, within reason, any quality EP that produces sharp, on-axis views will do a very nice job at planetary viewing, but most dedicated folk would agree that within this department, a decent Ortho is hard to beat. Unfortunately, Orthos have small eye lens, so eye relief can be uncomfortable for some, and, again, AFOV is usually quite very slight at 40º degrees or so.

It is for this reason, for example, that many other people prefer to choose wider field EPs for their planetary viewing, for hopefully, with these type of EPs, eye-relief is more comfortable and due to the larger AFOV, one doesn't have to be constantly turning their slow motion controls or nudging their dob scope. So, again, from this perspective there's nothing wrong with using a quality, wide field for planetary, perhaps a Radian, Delos Pentax XF or XW, and so on.

Ultimately, then, the eyepiece best for planetary is the eyepiece that which caters to your pocket and to how you enjoy viewing.

My final thought on all this is to slow down. You've only had a couple of sessions, so give it a little more time before investing in more astro-gear. I think the best plan is to slowly build a set of good quality eyepieces. Pay once and cry once. These will serve you in any scope you may happen to own in the future and will save you a few £'s in the long run. Perhaps set out on the 3 eyepiece + Barlow route I mentioned above and this will also give you a good idea of what high powers you think may be useful in future seasons.

[Reeny]

If your 8" dob is a Skywatcher, GSO, or Revelation, then the focal length will be 1200mm.

A 5mm eyepiece will be useful for less than 30-40% of the time.

Your most used eyepeice will be around 7 or 8mm (1200/8mm = 150x, 1200/7mm = 170x)

I use a 16mm Maxvision 68^o in a 2.2x barlow = 165x

It always delivers clear, sharp views before I change up to higher magnification.

The 7mm celestron will do that job for you.

You could try the Celestron first, then see if you need a wider view of around 68, 70, or 82 degrees for your 6mm option.

Note: the higher magnification makes the objects dissappear much quicker, so you will be nudging the scope more with 60^o compared to 68 or 82.

The 6mm Williams SPL has good reviews on the forum, at 55 degrees.

http://www.firstlightoptics.com/william-optics-eyepieces/william-optics-spl-eyepiece.html

But I would be paying the extra for the Explore Scientific 6.7mm 82 degrees at 180x mag and leave the 5mm until later.

Postage to Denmark might be a problem from ES - see the review section http://www.explorescientific.de/Okulare/

or get one here from the UK http://www.365astronomy.com/Explore-Scientific-Eyepieces/

[russ.will]

I'll second exactly what Reeny said and add that something around the 7-8mm mark is useful not only for planets, but duller more extended DSOs too. The 5mm would be an extravagance when you haven't really got got a workhorse in the 11-14mm range sorted yet too.

You said it was your second session last night. Is that with that scope, or ever? Has the scope been collimated or is it straight from the box? If it's the latter, you may be surprized how much even the stock eyepieces have yet to show you.

Russell

[alan potts]

Great advice already given, I cant better it. The Maxvision and barlow would be good , the barlow increasing the eye-relief of the 16mm which is a little tight for some.