Nexstar 8 with Televue 3x Barlow (Stars are blurry)

[Seb_]

Hi, yesterday I observed for the first time with my Nexstar 8 (Televue 3X barlow and 25mm Plossl celestron). After alignment, I installed the Televue 3x barlow and just by curiosity look a couple of stars like Vega, Altair, Capella and I can't really get a good focus. It was always blurry. Important notice to mention, It was about 4 degree Celsius yesterday and I didn't cold down my telescope.

Is someone can explain to me what could cause the blurry?

 

Thanks

[spaceboy]

2 things 1) x248 in a telescope that hasn't cooled to ambient temperature isn't going to give good results and 2) the seeing may have been to poor to allow such high magnification anyway. I know I went out a couple nights back and couldn't even look at the moon with only x64 the seeing was so bad. 

[Knighty2112]

You may have answered your own question there; you didn't let the scope cool down fully to the outside temperature. Ideally should leave it for 35 mins I believe the manual states.

[knobby]

Hi Seb, way too much mag unless seeing and transparency is very good and your scope has matched the outside temperature... my C8 takes an hour ish to be ready for much over 150 x mag.

 

[Seb_]

Thanks for your answer guys. The purpose of this High mag is that I want to try look at M83. If I only use my 25mm on M83, I see a really low spot of light but nothing more. I bought my Barlow to look at Planet but really curious what am I going to see at M83 whit 3x Barlow.

[spaceboy]

2 hours ago, Seb_ said:

Thanks for your answer guys. The purpose of this High mag is that I want to try look at M83. If I only use my 25mm on M83, I see a really low spot of light but nothing more. I bought my Barlow to look at Planet but really curious what am I going to see at M83 whit 3x Barlow.

I'm sorry to say it seems your another victim of glossy astro mags. I see a really low spot of light but nothing more that would be M83 and the same many other galaxies. Your not going to see anything like the images in sky at night or astronomy now as our eyes will only ever see a smudge of light in all but the very largest of telescopes. Using a barlow and high magnification on galaxies and nebula is going to make the views worse not better as your reducing the exit pupil. TBH the nights are few and far between that you could use x248 on planets as the UK seeing rarely permits magnifications above x200. A x3 barlow is not ideal for your scope and you would be far better off with a x2. You could try looking at the moon with the barlow 25mm combo but you will have to let the scope cool and hope seeing conditions are favourable.

[John]

The vast majority of galaxies look like small, faint spots or smudges of light even with my 12" scope. Using high powers does not usually add anything to the view apart from a slightly enlarged faint spot / smudge !

Still fascinating objects once you realise a bit about what you are looking at, how far away it is etc, etc but visually the views simply can't rival the images produced.

 

[Seb_]

Thanks for your comment guys. I bought the TV 3x for planet and plan to buy new eyepiece around 30 or 35mm to use with TV 3x

I'm leaving in Canada with no pollution light.

[John]

37 minutes ago, Seb_ said:

Thanks for your comment guys. I bought the TV 3x for planet and plan to buy new eyepiece around 30 or 35mm to use with TV 3x

I'm leaving in Canada with no pollution light.

Long focal length eyepieces don't tend to barlow well - the eye relief extends when the barlow is used so eye positioning becomes awkward.

Something like a 32mm plossl for deep sky observing with the scope would be a good idea though. Just don't bother using the barlow with it.

 

[Linda]

I have a similar scope. My most used eyepiece is my 24mm Maxvision 68 degrees, which shows the same field of view as a 32mm plössl as I have been told.

When I want to magnify, I use my 15mm GSO eyepiece, or preferably my 12mm ortho which is really sharp. But the atmosphere does not always allow for the 12mm to see anything sharp. I have an 8mm eyepiece that I have used at few occasions in my 5" scope to look at a planet. The eyepiece is the least used, because the seeing is seldom so good.

Galaxies, and many other DSOs are just faint grey fuzzies. And the more light pollution, the worse it gets. You can test magnification on stars beside the fuzzy. If they don't get sharp, then you better go back to less magnification. I can really recommend you to buy an ortho eyepiece, They're not expensive and are very sharp.

[Demonperformer]

It depends a little on exactly what you mean by "blurry", and certainly all the answers given so far could solve the problem, but I am going to mention a dreaded word ... collimation. If that is out, you aren't going to get nice pinprick points of light.

Once you have got the other things sorted, find a nice bright star high up and deliberatly defocus the scope slightly. If the rings that this produces are circular and concentric you can rest quietly, knowing that your collimation is good. If they aren't, you will need to come to grips with that. But, as I say, sort all the other stuff first.

Thanks.

[cloudsweeper]

All good points.  I had a similar experience with my 8" Celestron recently - tried to use it too soon, and stars were blurred.  Half an hour later it was fine!

Doug.

[Peter Drew]

There are nearly always problems to overcome before you get a good image, with Barlows try to think in terms of 2x Barlow as being 2x the problems, 3x Barlow 3x the problems and so on. 

[spaceboy]

6 hours ago, Seb_ said:

Thanks for your comment guys. I bought the TV 3x for planet and plan to buy new eyepiece around 30 or 35mm to use with TV 3x

I'm leaving in Canada with no pollution light.

Don't get seeing confused with light pollution. http://www.skyatnightmagazine.com/feature/general-guide/guide-seeing-and-atmospheric-transparency

You can have perfectly dark skies but if those skies are turbulent then you will get blurry views at high magnifications.

Personally I would not get too hung up on the x3 barlow. Beginners to astronomy are under the delusion that magnification is everything when it comes to telescopes but this is not the case. You would be stunned to hear how many newbies ask why they are getting blurry images and after some Q&A's it's found that they don't even go out side and think there is nothing wrong sat in a warm house stargazing through a window.

[Seb_]

36 minutes ago, spaceboy said:

Don't get seeing confused with light pollution. http://www.skyatnightmagazine.com/feature/general-guide/guide-seeing-and-atmospheric-transparency

You can have perfectly dark skies but if those skies are turbulent then you will get blurry views at high magnifications.

Personally I would not get too hung up on the x3 barlow. Beginners to astronomy are under the delusion that magnification is everything when it comes to telescopes but this is not the case. You would be stunned to hear how many newbies ask why they are getting blurry images and after some Q&A's it's found that they don't even go out side and think there is nothing wrong sat in a warm house stargazing through a window.

 

I'm a beginner but I did my basic homework. I bought the X3 Barlow to learn and understand witch kind of view I will get. I'm very lucky to not be on a tight budget so this is why I bought it. So far I bought the TV 19mm Panoptic but I realize that I will need more eye relief because I wear glasses.

 

I asked a question on this forum about what exactly happened when you increase magnification, this is why I though I will see more on M31. I though I will see more stars so a better shape of the galaxy.

 

Here the Quote

 

On 7/7/2016 at 18:04, Stu said:

Jetstream's answer is a good one, but here is my take.

Magnifying a star does not make it brighter, nor will it will not appear dimmer at higher magnification. Increasing magnification dims the sky background (which is effectively an extended source) and so a star which was lost in the background now becomes visible.

Note that when you magnify to an extreme degree, bright stars will appear larger as you effectively see the airy disk. You are not actually seeing the star as a disk, merely enlarging the optical effect which is the airy disk. At that point, we are beyond the scope of this discussion and it's not necessarily at a level you would be operating your scope at regularly anyway.

Note also that this is an extremely complex area which many of us still struggle to get our heads around. For every rule there are exceptions and differences in people's eyes change outcomes too.

 

]

[spaceboy]

I'm very lucky to not be on a tight budget so this is why I bought it. So far I bought the TV 19mm Panoptic but I realize that I will need more eye relief because I wear glasses. If you wear glasses and your flexible with your budget you ideally need to choose eyepieces that allow for longer eye relief. Most manufacturers websites list this in the parameters of their eyepieces. In this case I would have recommended the 17T4 nagler over the 19 pan. Using a barlow to increase eye relief is not the way to go as it pushes the eye relief beyond the design of that eyepiece and in doing so you will struggle to get eye position correct with out experiencing kidney beaning, black outs or a loss of fov.

Magnifying a star does not make it brighter, nor will it will not appear dimmer at higher magnification. Increasing magnification dims the sky background (which is effectively an extended source) and so a star which was lost in the background now becomes visible.

Note that when you magnify to an extreme degree, bright stars will appear larger as you effectively see the airy disk. You are not actually seeing the star as a disk, merely enlarging the optical effect which is the airy disk. At that point, we are beyond the scope of this discussion and it's not necessarily at a level you would be operating your scope at regularly anyway.

The above quote makes no sense to me but then I am reading it out of context and have no idea what was said before hand ???? Magnifying a star will not make it brighter but it will make it dimmer depending on your scope and eyepiece used. This is due to exit pupil. The higher the magnification the smaller the exit pupil and the less the light that reaches your eye. Increasing magnification does darken the background sky but for the reasons just said. I will have to let someone else comment on the magnification thing. I did read a discussion on this which made sense but cannot remember it off the top of my head. It was something along the line of magnification increases the size of an object but it doesn't make it closer so your always going to be limited by the resolving power of your telescope. IE: bigger mirror / lens more detail.

[Seb_]

Thanks spaceboy, here the original post. 

 

[spaceboy]

Scrub my understanding of sky darkness with magnification. The thread you posted basically tells you what you need to know just know which post to not get too hung up on