Various ep questions

[Fey]

Hi all.  I have a Skywatcher Heritage 100p and am looking for advice on new eyepieces.  Until  now I have been using the ep's that came with the scope - 25mm and 10mm with a 2x barlow.

I would like to get a higher magnification lens for clearer views of planets and a lower mag for clusters and nebulae.  I have had some great views of Jupiter with the 10mm and would like some more detailed views if possible.  What would be suitable sizes for my scope (focal length of 400mm, f/4).  I have read that fast scopes like mine are unforgiving on eyepieces.  I have been looking at Revelation ep's, as these are within my budget range and seem to have good reviews.

I also would like to know what is the best method for cleaning ep's.  One of mine seems dusty and I need some good advice before I clean it.

Finally, is there any advantage of having a 2.5x barlow over a 2x or 3x

Thanks in advance for any advice.

Fey.

[laudropb]

Your 100 mm mirror will probably mean your highest usable magnification will be about 150x. In theory it is 200x, but given the atmospheric conditions you will seldom achieve this. Your scope is f4 and this low focal ratio generally means you have to purchase better quality eye pieces. The advantage of purchasing a 2.5 Barlow, such as the revelation, is that it will be of much better quality than the one supplied with the scope. Sorry if this all sounds a bit negative. The Heritage 100p is a fine scope and I would add that higher magnification does not always equal a better view. This can be achieved by better quality eye pieces.

[Fey]

Thanks for the reply, it doesn't sound negative, just realistic.  I am aware that a higher magnification ep doesn't necessarily mean a better view.  I am hoping that by buying a better quality eyepiece of around 6 or 7mm and a 2 or 2.5x barlow will give me clearer detail.

[bomberbaz]

I have the same scope as a grab n go and I find that the highest magnification useable is around x100. Thats more down to OTA stability and a not very good focuser over anything else.

That said it is a cracking little scope and I have used it on a few occasions to grab early morning special moments when setting up the large scope is out of the question. 

Steve

[Charic]

My advice is that the size of the aperture some way dictates the telescopes capability?
Your scope features a Focal length of 400mm, 100mm of Aperture resulting in a focal ratio of f/4.
Using a 4mm Eyepiece you would achieve 100x power, matching the aperture, and your scope is designed for this, yet  asking for more power will actually degrade the image rather than improve on it?

Try the 25mm on its own against Jupiter then  Barlow it (  now  12.5mm)  then swap out for the 10mm then Barlow that ( now 5mm) The image will appear bigger each time, but note,  it does not get any sharper, infact the reverse is often true, the longer the focal length of the eyepiece, the sharper the image, but that image is oh-so tiny!

To get the detail you so desire may entail getting a bigger scope! also one with a longer focal length?
I would not buy a specific 4mm eyepiece for this scope, an 8mm 2xBarlowed would be my option, or be satisfied with the 10mm Barlowed.

You may think a new eyepiece alone will make  all the difference, but  do consider the whole set-up in order to better the images you wish to see. I have an 8mm that retails just off £50 and an 8mm that retails just of £300? They do the same job, providing me with 150x power,  the field of view is wider on the dearer EP, but not much more is apparent to my eyes, at present from my observing site, with local light polluted conditions.
On a bigger, faster scope, there should be a more noticeable difference as to the quality of the dearer EP,  I hope!

As for the 2.5 Barlow. That will just sit midway between the other two, I see no real advantage of one over the others, its down to personal choice. I did  once own a 2.5x Barlow, but replaced that with a 2xBarlow, preferring the lower power, and the inbuilt DSLR  'T' connector facility and also the  removable lens cell, so I can get as low as about 1.5 - 1.6x Barlow!

HTH.

[Pig]

Hiya Fey,

I think the guys above have pretty much covered the eyepiece selection question  As for cleaning your eyepiece a popular choice is Baader optical wonder fluid and cloth:-

http://www.firstlightoptics.com/astronomy-optics-cleaning-protection/baader-optical-wonder-fluid.html

And / or:-

http://www.firstlightoptics.com/astronomy-optics-cleaning-protection/celestron-lens-pen.html

Do not be tempted to take your eyepieces apart unless you know exactly what your doing as there can be quite a few lenses and spacers, all of which will need to be put back and in, in the correct configuration.

[jetstream]

One of these and one of these (10mm) would work well for you http://www.firstlightoptics.com/baader-planetarium/baader-classic-q-225x-barlow.html , http://www.firstlightoptics.com/baader-planetarium/baader-classic-ortho-bco-eyepiece.html