Problem with Barlow

[Pasiya]

Hello,

One month ago I bought my very first telescope - Skywatcher 150/750.
With my telescope came 2x Barlow lens which I used to observe Moon two nights in a row. It was perfect. After, it became really cloudy and it took me one month before I could use my telescope again. For that time I did not use my telescope. I only kept testing my mount to learn more about GoTo system.

So, after one month, I was finally able to see Moon again and upon inserting Barlow, Moon became bright, smudged, white ball. I was not, nor I am now, able to focus with it.

My friend tried inserting his Barlow - which works fine on his Skywatcher - but on mine the result was the same.

Everything else works fine but Barlow.

I tried searching on net but nothing really helped.

Does anyone know what am I doing wrong?

[Dave In Vermont]

What eyepiece are you using with the Barlow? Having something not come to sharp focus is what can be anticipated if using too high a magnification for a.) The telescope. b.) The 'seeing' conditions. c.) Both.

To find the magnification you are using you divide the focal-length of the eyepiece by the focal-length of the telescope - both expressed in millimeters. So a 6mm eyepiece in a scope with 750mm FL = 125X. Add a 2X Barlow and you have 250X. And this is approaching the maximum magnification many astronomer's would recommend.

'Seeing' is the actual condition of your sky, taking all factors into account including upper-air turbulence, dust and/or smoke particulates, humidity, etc. Even ifthe sky looks crystal-clear, the 'seeing' can be poor. And a poor-appearing sky can actually have very good 'seeing' conditions through the telescope. It's tricky. Experience helps.

Hope this helps and do let us know. Meanwhile:

Greetings and welcome to SGL, Pasiya! Nice to have you aboard.

Clear skies -

Dave

[Knighty2112]

Test the Barlow in your scope in the daytime if possible. If the optics are not right in it because of any knocks then you will struggle to reach focus in the daytime too. The brighter the day light the better to test it with too.

[bingevader]

And/or the barlow in your friends 'scope too if he doesn't have any problem with his.

[Laurie61]

If the barlow/eyepiece combination worked first time it still should, it might be worth checking collimation to see if it's moved.      

[Peter Drew]

Also, if the Moon was "full" at the time it is much harder to get a detailed image.  Welcome to SGL Pasiya.   

[Pasiya]

Thank you everyone for warm welcome and fast replies.
Happy to be here.

I am using 10mm and 25mm that came with my telescope.
When it happened, the sky was pretty clear. This is the photo I took that night: http://sta.sh/093ogpkj1zr. It was taken with my phone . As you can see, the Moon was not full and not too bright.

It really looked weird but not in a 'out of focus' way. Honestly, it looked like bright disk. The surface was smudged and so bright that I could not look at it.
The closest that I can explain is that it looked like I am watching at our Sun trough filter. Something like this: http://sta.sh/0odr37mvimm, but more bright.

Then the 'odd' happens. I remove my Barlow and insert 10mm eyepiece again (without Barlow) and the Moon would still look like disk. Then, I would simply remove 10mm eyepiece and insert it back again, and it would look normal.
I tried collimating my telescope and cleaning the lenses but it did nothing.

At first I thought change in temperature was too hight and scope needed some time to adapt. So, I kept it out for 2 hours aaaand it did not help.

I am trying to figure out what triggers it, so I can stop doing whatever I am doing.

 

[Dave In Vermont]

For one thing - stop cleaning your lenses. That can actually damage the coatings if not done in certain specific ways (which you can learn here). You have clarified the list of suspects of what's causing your difficulty. It sounds like it was simply too bright to get a good view. Most of us here don't bother with viewing the Moon when it's full, or close to it. Except during a lunar eclipse. The best times for lunar observation is when it's less full. And the best places on the Moon are along the line between the lit and unlit section - which is called the lunar-terminator. Or just the terminator.

And there are filters available to reduce it's brightness to a more manageable level to get a beautiful, high-contrast view. But more on this is available elsewhere. What I suggest that you do now is to not aim the telescope at the Moon until it's further from being full. Instead, try aiming the scope at a star - any star - and focus it to as sharp a pin-point of light that you can each eyepiece. Then attach the Barlow and re-focus again. Let us know what you see. I'm betting you'll just see the pin-point light from your chosen star. If my guess is correct, your problem is solved!

Please let us know once you've accomplished this.

Enjoy!

Dave

[Pasiya]

Tonight I had a chance to use Barlow again and it is 'working'. If I ever get the problem again, I wil make sure to record it.

Thank you all for reaching out to help me!

 

[Knighty2112]

Your main telescope cap should have a smaller aperture that you can open in it to allow less light into the telescope, so this might help reduce any glare from a bright moon. As stated, most astronomers don't observe the moon when it it too full as it is simply too bright to be able to get any decent view of any detail, except for some of the bright seas or craters with bright Ray system coming off them. Best to observe the moon along the terminator line when it is waxing and the waning, but mostly never past 3/4 full as it is then simply too bright.

Telescope end cap

With smaller cap removed