Not focusing properly

[LeaWoo]

Hi All,

Happy Sunday!

Recently purchased a Skywatcher Mercury 707 az and we've found Mars pretty quickly, the image is good, however it doesn't seem to be focusing very well. We have a 10mm, 25mm and a x2 barlow lens. Could it be the eye pieces? Any advice please?

[DaveL59]

which eyepieces are you using when you aren't getting good focus?

You should be able to get crisp focus with the diagonal and the 25mm eyepiece, the MA10mm should give more magnification but isn't the best. Not sure which barlow is supplied but that can affect image quality if its an all plastic affair.

Is the focuser smooth or quite stiff as that can make a difference when making small adjustments. If its very tight then you can ease this by slackening the 2 screws under it just a touch till it suits your needs.

[LeaWoo]

Hi, thanks for your response.

After a play around, the focus is as it should be, but it is almost like it is zoomed in too much with each eyepiece we use.

Rather than seeing the whole planet in view, we can just see a part of it. I hope I'm making sense?

Is this to do with the eyepieces we have?

Edited November 15, 2020 by LeaWoo

[DaveL59]

For Mars that'd be surprising, or any planet for that matter. I believe your scope is a 70/700 so much the same as the Celestron I have. With the 25mm eyepiece you'd get x28 and the 10mm would give x70. The barlow would double those figures but even at x140 the planet should be well inside the field of view and quite small.

Only way I can think it would fill the frame would be if out of focus where it'd become a larger fuzzy ball. In focus it'll be at its smallest in the eyepiece but also at its sharpest if you see what I mean.

[John]

I suspect you are well away from sharp focus as suggested above. Mars will look like a very small pink disk perhaps with vague dark markings on it even at the maximum power you can get, eg: 10mm eyepiece plus 2x barlow lens. Something like this:

 

[LeaWoo]

My partner saw Mars' scar yesterday so we are certain it's Mars. It seems to focus on one small part of the planet and then the outer part is blurry, but no matter how much we play with the focus it doesn't seem to change or improve. 

I feel we are doing something wrong here but I don't know what.

[John]

3 minutes ago, LeaWoo said:

My partner saw Mars' scar yesterday so we are certain it's Mars. It seems to focus on one small part of the planet and then the outer part is blurry, but no matter how much we play with the focus it doesn't seem to change or improve. 

I feel we are doing something wrong here but I don't know what.

Not sure what Mars's scar is but the image that I have posted is what Mars looks like with a smallish scope at the max magnification that you will be able to use with the eyepieces and barlow lens you have.

 

[Ed in UK]

I was looking at Mars last night but would have struggled to make out any detail. The planet will appear like a bright red/orange star at 25mm and a small red/orange disc at 10mm. Both images should be relatively sharp. When out of focus the planet will appear as a fuzzy ball. Are you sure that you have the eye piece sitting in the holder correctly ? 

With my limited knowledge it sounds like you have a focusing problem.

If you can use your scope during the day have a look at a distant object such as a tree or a building and make sure that you can get that in focus.

If you can't use the scope during the day then use the moon. Again check to see if you can obtain focus. Stars should appear as pinpricks of light and not fuzzy balls.

Let us know how you get on.

Good luck.

[reezeh]

I'm not familiar with your model of telescope, but some either have an extending drawtube or extender. Could it be that you need to use one? 

[LeaWoo]

On 26/11/2020 at 10:11, Ed in UK said:

I was looking at Mars last night but would have struggled to make out any detail. The planet will appear like a bright red/orange star at 25mm and a small red/orange disc at 10mm. Both images should be relatively sharp. When out of focus the planet will appear as a fuzzy ball. Are you sure that you have the eye piece sitting in the holder correctly ? 

With my limited knowledge it sounds like you have a focusing problem.

If you can use your scope during the day have a look at a distant object such as a tree or a building and make sure that you can get that in focus.

If you can't use the scope during the day then use the moon. Again check to see if you can obtain focus. Stars should appear as pinpricks of light and not fuzzy balls.

Let us know how you get on.

Good luck.

Thank you for your input.

 

We returned the telescope due to a fault and are currently looking for a new one. Everything seems to be out of stock at the moment!

[happy-kat]

On 26/11/2020 at 11:14, reezeh said:

I'm not familiar with your model of telescope, but some either have an extending drawtube or extender. Could it be that you need to use one? 

The OP had a refractor, so a diagonal should have been supplied with the telescope.

Hopefully the next telescope will prove useful to them.