Help with viewing

[shedman]

Hi all, Bought a scope about 3 weeks ago. It is a Helios 4.5" reflector, it also came with a 2 x Barlow and 2 other eyepieces these being an H20mm and an H8mm. Are these good enough for viewing objects or do I need to purchase anything else. Been out tonight and got some great views of the moon and picked up Jupiter but I seem to have such a small focal range on my main lens before I lose the image am I doing something wrong?

[Catweazel]

Hi, if you use the 8mm with a barlow it may be too much mag for the scope. When you say that you lose the image, do you mean lose focus? or that the image moves out of view in the scope? Which eyepieces were you using to view Jupiter? CW

[Capricorn]

I believe that the eyepieces mantioned have a narrow field of view.

So whatever you locate will rotate out of view pretty quick.

With 2 eyepieces you do not have much choice.

If feasible then look at purchasing a couple of additional eyepieces, plossl's are readily available. Not sure of the specification of the scope, focal length so not going to suggest anything specific in terms of eyepiece focal lengths.

If I remember the H designation means Huygen type eyepiece.

These work best with long focal length scopes and I suspect yours isn't.

They are pretty simple eyepieces and have short eye relief, plossl's are a fair advancement.

[hemihaggis]

once you have a ep in the scope , you focus it ..... if you swap for an other ep , you will have to re-focus .

the objects you are observing apper to move as the earth turns .... so they drift out of view

[shedman]

Thanks for your helpful hints. I was using the 20mm eyepiece along with the barlow for jupiter but my focus range is so small that just the smallest adjustment and I lose the image.Is that normal?

[brantuk]

On most scope just 1mm either way and it will go out of focus. For finer adjustment some scopes use a DS (dual speed) focuser with gearing that steps down 1 in 10 - meaning the focus wheel moves less with each turn of the knob.

To work out the magnification divide the focal length of the scope by the focal length of the eyepiece. Most nights in the UK 200x is a realistic maximum due to atmospheric conditions. I find the most I can comfortably use averages out at 150x to 180x.

Choose a very clear night like tonight, and high objects so you are looking through less atmosphere. Give the scope 1/2hr to 1hr to cool down and you'll find you can maintain focus longer.

With a 4.5" scope the brighter objects will be easier to see. Try Jupiter (and moons), M42 in Orion, Plieades, M31 in Andromeda (early evening), and leave the Moon till last cos it's bright and will wreck your night vision.