Zoom eyepieces - any good

[Steve-hobart (Steve)]

Im just getting my first scope (10" dob) and starting to think about additional bits such as eyepieces and filters.
I will probably want a high mag eyepiece ( say a 4mm) but have seen there are zoom ones available ( not 4mm) and just wondered if they were any good. I assume a non zoom is probably better from a pure optical perspective but the zoom would be convenient...
Anyone had any experience with the zooms?

[barx1963 (Malcolm)]

Congratulations on the scope, 10" is a great place to start
My usual advice for new scope owners is do not be in too much of a rush to get bits and bobs until you have used the scope a few times and understand its limitations and strong points.
Before delving into eyepieces, can you tell us what ones your scope comes with or if you have any at the moment? If I assume it will come with a pretty standard pair of plossls say 25mm and 10mm and is a standard f5 dob, you will have powers of 1250/25 = 50 and 1250/10 = 125x. For most observing that is more than adequate. In my 12 inch I did almost all my observing with a 24 and a 13 giving 62x and 113x. Other EPs were used maybe 5% of the time at the most. Remember, higher power is not always betterm and a 4mm at 312x is going to be nearly unseable on all but the most exceptional nights in a 10". More power dims the image and also magnifies distortions and atmospheric intability.
Also with zooms they are certainly better these days than early ones but I am of the opinion that a set of 2 or 3 good quality prime EPs will beat any zoom out there.
With filters again, use the scope and decide where interests lie. Coloured ones are really only for planetary use, OIII are for planetary nebs. A general nebula filter is handy but not essential.
More beneficial things are charts, red lights, a good lightweight table, an observing chair and given you are in Hobart, dew protection. Also collimating tools. All of these are going to make life at the scope ,ore pleasant than filters and eyepieces.

Cheers

Malcolm

[Steve-hobart (Steve)]

I hadnt thought much about dew. What do people normally do with a fixed tube dob?

[glend (Glen)]

Having purchased a 12" dob recently and gone through this I would suggest you read everything you can about eyepieces here on IIS before you go out and purchase something. Eyepieces in the 4mm range can be hard to use if you need significant eye relief. There are some very good wide field eyepieces in 30mm which make using the dob much easier particularly when locating things and then go to more powerful narrow field EPs to get more power.

Also look into putting an azimuth circle on your base and get an inclinometre so that you can find objects easily and not have to star hop every time. With a properly aligned scope with setting circle and inclinometre you will be able to go right to the object location and then using the wide angle EP close in on it and centre it before going to a higher magnification.

Read the Dob Mod postings here and there are a number of setting circle files available that you can simply print and laminate to attach to the base. Build yourself a leveling base, this is a good mod to ensure you can level the scope during alignment so your co-ordinates are correct.


BTW what scope are you buying?

For dew management there are things that can be added to the scope and right now (winter) dew is a problem most nights. Your scope may have a fan behind the mirror and this can help keep dew off the mirrors if you use it to control the temp. Also you can make a dew shield to fit over the end of the scope and this helps as well. Then there are mirror heaters if you need to go that far.

[Steve-hobart (Steve)]

Getting a skywatcher 10" (they had them on special via Aus Geographic for $599 which avoided $200 in shipping). It comes with a 25mm and 9mm from memory.

[glend (Glen)]

You can get your setting circle pdf files here:

http://www.cloudynights.com/ubbthrea...umber/1733251/

any Officeworks can print and laminate them for you. Check the diameter of your base just to be sure it is going to fit ok.

[Wavytone]

Steve,

If you aren't sure about eyepieces then stick to say 3 cheap ones for now, on the basis that later on when you know more, maybe buy a set of really good ones after you have had the chance to borrow a few to see which ones you like in your scope. Different observers have different preferences and what works well in one scope doesn't always work well in others.

For your dob a set of 3 Plossls are a good start and will cost much less than a good zoom.

As for... zooms.

This http://www.cloudynights.com/item.php?item_id=2146
and http://www.cloudynights.com/documents/zooms.pdf

cover all the zooms made in recent years. The Leica, Nikon, Televue are probably the best, in that order. The Vixen and Baader ones will probably have you reaching for eyepieces.

In principle the idea is to cover the range 8-24mm, equivalent to 3 eyepieces. But with zooms, the compromise you make for this is narrower field of view and more glass (weight and light loss) than in good widefield eyepieces.

[barx1963 (Malcolm)]

Steve
With dew, the primary mirror will usually be OK but the secondary and eyepieces can fog up very quickly short term you can take a hairdryer with you if you have power and use it to defog (with the secondaty take out the eyepiece and blow doen the focuser. A bit clumsy and the neighbours may wonder what is going on but works.
Long term a dew constroller and set of straps works best. You can get heaters for the secondary as well. Check out http://www.bintel.com.au/Accessories...egorylist.aspx

Malcolm