Questions about My EPs

[rabbithutch]

My kit includes an older (1990s) 8" Orion newt on a dob mount. It is the model where the secondary mirror is attached by a single spider (or should that be spyder) vane. It has a focal length of 1219 mm (48") and focal ratio of f/6. These stats I get from the manual that came with the scope.

My EPs are a Plössl 7.5 mm by Sirius, an OR12.5 mm by Meade, a Plössl 26 mm by Sirius, and a 24.5 mm super wide angle by Meade. This is the information taken from the EPs themselves. Now it's time to reveal my true ignorance. All are 1.25".

First, from reading, I learn that "Plössl" defines an EP with optical elements based on the design of Georg Plössl sometime in the 19th Century. I read the wiki and saw the diagrams. So, I know that 2 of the EPs listed above have those optical elements.

The OR12.5 mm Meade EP looks very different in that it has a smaller viewing aperture diameter. Is there anywhere I can find out about the optical elements in this EP? If it is not a Plössl, what design is it? What attributes does it offer for viewing that the 7.5 mm Plössl doesn't? Do I understand correctly that the 7.5 gives higher magnification than the 12.5 mm - or does that depend on the optical elements? If I'm correct about the 7.5 vs the 12.5, then how does one determine how much magnification each gives? (My understanding of the term "magnification" is the apparent size of the image seen through an EP, eg, 20X or 70X or 200X.)

From actual use, the 24.5 mm Meade super wide angle gives a different field of view; but I know nothing about the EP. I've guessed that the optics must be of the Nagler type but don't know this. How can I find out?

I keep the EPs in a closed plastic case that came with the scope. There are holes in the foam padding within that the EPs fit into. I also have digital angle finder, my filters, and my Telrad in this case when the scope is not in use. I have no caps to cover the ends of the EPs. Should they have protective covers? Or, would that be over-kill given their storage in a closed case? Should I clean them occasionally? If so, how? What materials should be used? Would using the same type cloth one cleans monitors a computer monitor or TV screen and the same glass cleaner be harmful? I have used a lens brush on them but never tried to clean them.

I don't have a Barlow. My understanding is that a Barlow works like a teleconverter for a 35 mm camera lens and is rated as 2X or 3X meaning that the Barlow doubles or triples the magnification. Is that the case? Could someone point be to pictures of Barlows and especially how they are mounted in conjunction with an EP? Should I consider buying a Barlow given the set of EPs I have? What brands are better than others and what do they cost?

Finally, I would appreciate comments on the quality of the pieces I have. Are they from the low-end (ergo lower quality) of the quality spectrum? Mid-range? What would I gain by purchasing replacement EPs and what would you recommend? I am too new to viewing and to using equipment to make any relevant qualitative judgments, but I would like to know if there are worthwhile benefits to pursue by having better EPs. (My suspicion is that having higher quality EPs would be wasted on this scope - that I would need more aperture or better mirrors to uncover the limits of these EPs).

Thank you for your time and attention. I would really appreciate your comments to help me learn about my gear and its care and feeding.

Cheers!

[rowan46]

as to the eyepieces, google is your friend, google the numbers you have and then look for images, cloudy nights has lots of threads on classic eyepiecesyou may find something on there. magnification is calculated by the focal length of the scope divided by the eyepiece eg.1219 divided by 7.5 equals 162x.

A barlow is mounted into the focusser and then the eyepiece mounted on top.

To clean your eyepieces use Baader wonder fluid but first blow off any loose debris or grit if they are really bad sluice the tops with distilled water as wiping eyepieces dry is a good way of scratching them, many eyepieces have various rare earths as a coating so its not a good idea to use anything but good quality optical cleaner for them.

As you are fairly new to astronomy my guess is you have not collimated your scope yet get a collimator cap or laser and collimate it, this will make a big difference to the view after it's collimated you may be better able to assess your eyepiece quality and do at least get some bolt cases for your eyepieces.

[twotter]

I would guess the Meade OR12.5mm could be an orthoscopic. Does it look anything like the 7mm in this review on Cloudy Nights?

7mm Meade Research Grade Orthoscopic (Peer Reviewed) - Review

[AndyH]

Does the meade or(ortho) 12.5mm have a flat top or does it have sloped sides, commonly refered to, as a volcano top? They actually had three versions of orthos for sale, years back. Two of those had a 12.5mm in the list.

Here's a pic of an ad in the November 1982 edition of Astronomy magazine.

Stargazers Lounge - AndyH's Album: Retro Astro adverts - Picture

The orthos are items 18, 21 and 22. The 22's are the research grade orthos and are distinctive as they have a lightweight aluminum barrel.

This might help,

Eyepiece - Wikipedia, the free encyclopedia

and this,

http://stargazerslounge.com/primers-tutorials/63184-primer-understanding-choosing-eyepieces.html

A review site, which I like and is handy for reviews of older stuff,

Excelsis - EquipmentReviews

An ortho is a cracking design. Old fashioned, but still well loved and respected for it's sharp contrasty views. As with all eyepieces it has it's downsides. Small eyerelief and small field of view. It'll give you 98x mag in your scope and if you could get a good quality barlow, say one at 1.8x, would convert this 'piece to 176x(good high power for planets and moon). You slip the eyepiece into the barlow, then fit this combo into the focuser.

The sirius plossls are probably decent. Not brilliant but not awful. I had a 26mm one and it was okay.

Never used a Meade super wide angle, so can't comment.

As for cleaning, I couldn't do without a hurricane blower(rubber puffer that you squeeze to blow out air) to blow off dust/particles and some good quality spectacle or lens cloths. I personally clean eyepieces by very carefully blowing my breath on the lens and some gentle wiping with a clean part of the cloth. I only use specialist optics cleaners on scope lenses if needed. Use the rubber blower first.

You can pick up caps quite cheaply and will be an extra layer of protection for the eyepieces.

As for other eyepieces to mate your scope, something to consider is looking out for eyepieces with wider afov(average field of view), which will be easier to keep the object in view on a dob type mount.

:icon_salut:Andy.