BST 8mm Wide Angle first nigth...

[owen1024]

Hi,

I've just come back from a quick session to check out my new 8mm Wide Angle BST EP on a Skywatcher 200P telescope. Time was limited so I only had 15 mins or so viewing Saturn, but I found the whole viewing experience a bit poor. I'm finding it hard to know if my expectations are too high, I'm doing something wrong, or the optics are less than perfect is some way. Being a complete beginner and not having a point of reference to refer to it's hard to know which of the above is in effect.

A little background:

Since I've had the telescope (~10 months) I've always used the 25 mm EP with or without the Barlow for everything. I found the 10mm that came with the scope unusable for anything as I can never get it focused. I've collimated the telescope (I think) which did improve things a little.

As I say without a frame of reference it's hard to unpick what is wrong (if anything). So I'll try and describe what Jupiter was like through the scope back in Dec/Jan when it high in the sky and as I understand about as good as it gets. I'm lucky enough to have access to a farm that's about 10 miles from the nearest town so in terms of light pollution the viewing conditions are pretty good (for Kent). Viewing Jupiter through the 25mm wide angle with or without the Barlow, the view is about the same in terms of image quality. Obviously with the Barlow there is more magnification but the image quality is lower. Either way I just about see there is banding across the planet but it's right on the edge of being visible, the bands are definitely not clearly defined.

The viewing experience (although not looking at Jupiter this time round) with the new 8mm EP is no better than the stock 25mm if anything it was a little worse (with the Barlow I could not get focus with the 8mm)

any comments, thoughts, advice would be gratefully received.

Thanks

O

[Andy_E]

Sounds like poor viewing conditions to me. Saturn is VERY low in the sky at the moment and isn't visible when it's dark. You'll have to wait till 2014 if you want to try for a decent view of Saturn. For observing solar system objects (bear with me, I'm a DSO man myself) it's not just dark skies that matter; the clarity of the atmosphere in terms of air disturbance is very important. unless the atmosphere is wonderfully still all you'll be doing is magnifying the turbulence, hence the higher power EP you use the poorer the view. Best ignore planets for the moment and try it out on some appropriate DSOs... M57 and even M13 will hold up very well to this sort of magnification and will let you get to know your new EP much better. Hope this helps... I'm sure there will be plenty more replies!

[John]

Saturn is low at the moment which won't help. It's also possible that your scope is not in good collimation as that will affect the clarity and resolution of the image a lot. You also mention that it was a quick session - an 8" scope takes a good 20-30 mins to cool to the point where reasonable high power views can be had. 40 - 60 mins are needed for it to fully reach ambient temperature.

It's unlikely that your optics (either the scope or the eyepiece) are actually faulty. It's much more likely to be either trying to view Saturn too close to the horizon, the optics are out of collimation, not completely cooled or a bit of all three perhaps.

[wookie1965]

Ive always got a good view of Saturn with my 8mm BST weather conditions permitting as said above Saturn so low now there is a lot of turbulent air, i tried the other night and it was not that good but m57 high up as brilliant, check collimation i do every time my scope is f5 that is why i check and go for objects higher in night sky less turbulence.

[ronin]

Saturn and Jupiter are in poor positions at this time, Jupiter should get better, just not immediatly.

200P's need some time to cool down and reduce the air currents that will be created around the mirror, especially those at the nice shiny surface. I would suggest trying to leave the scope a bit longer to cool down and then go hunting for something higher up to see how the scope and eyepiece perform together. Albereio, Double Cluster are both fairly positioned and should give a truer indication of how well they work as a pair. Try the Ring Nebula in Lyra, M57, probably a few things in Cassiopeia as well.

To repeat others collimation will be a factor on the scope, so although you have checked it still suggest you go over it at least in youir mind that everything was done right. Not exactly uncommon to make a good situation worse as I think sometimes we simply get the image through the collimator right without knowing what the underlying situation is.

The collimation guides say that if collimation is correct then this is what you is X, Y and Z, the assumption being if you see X, Y and Z then collimation is correct. I am not convinced that the second presumption is always correct.

If you are a member of a club then ask to have a look through someone elses similar scope, if it is the same as yours then it the scope is most likely OK and the BST. Just make sure it is a similar scope and not one costing 3x as much. Owing to the images we see of things expectations are often initially a bit high. But it is strange how 2 different sciopes can give very different views and not always the best view from what is the "best" scope. I have direct experience of this.

Will mention that many say that reflectors give a "softer" image, they collect the photons but that could be at the expense of a little sharpness and contrast. I don't own one to be able to say from personel experience. However it is back to the fact that no one scope does everything ideally.

[scuffer]

Could be your expectations , the banding will not be as clear as you see in pictures , the 8mm will show it better , with the 25mm it could be to small . I would wait for the moon to come up and try the different combinations on this also do a star test for collimation

[Singlin]

I don't live in the uk but since the middle of last week the jet stream winds have been very strong and seeing has been terrible.

I hold sessions in the evenings for my clients of the Hotel and cancelled them on Wednesday until last night where I started imaging the Bubble Nebula.

I also use the 8mm BST ED and get excellent views through it on my 10" f4 Quattro.

I would wait for the seeing to get better.

[NGC 1502]

You have some great advice above. Willing to bet that the SW scope and BST eyepiece are fine.

So from previous posts -

Collimation.

Cooldown.

Don't view close to horizon and expect good views.

The faint objects are heavily affected by light pollution (get out of town, if you can).

Realistic expectations.

Hope you sort the issues and your next session is good.

Regards, Ed.

[rwilkey]

Unless you wear glasses, I find that using the 8mm BST is best used with the twist-up eyecup fully extended, try this if you can. Otherwise I agree with others, Saturn and Jupiter are not at their best positions at the moment, they would have been much better back in Dec/Jan when you last viewed, also you need time to view properly, a quick 15 mins will not be conducive to good viewing.

[astrosathya]

The stock eyepieces that came with the 200P are one or the other form of the Kellner design, with one of the two lenses being an achromat. Kellners and their derivatives are good to use on telescopes of long focal length. As the focal length decreases, the optical design needs to get a little more complicated to handle the incoming light better. BST eyepieces are good for what they cost. They have a better design, (mostly Nagler/wide angle clones), but for the price you pay, you will only get the basic glass in its optics. High magnification requires good optical quality, not only in design, but also glass and coatings. Why is it that a Tele Vue delos will cost you an arm and a leg for the same focal length? They most likely use exotic glass, at least low dispersion glass of some sort, are made with care, coated thoroughly on all surfaces and so on. High magnification viewing of planets is very demanding in terms of eyepiece quality and collimation of the main telescope. I have the 200PDS as seen in my signature, and I also have an Antares 5.7mm 70deg FoV eyepiece that I use for planetary.

I prefer to use eyepieces for high power views, and not combine them with barlows. Why? Because the eyepiece (8mm focal length) has such a small focal length, even if it has an apparent FoV of 70degrees, when combines with the main telescope, without a barlow, the True FoV is 0.56 degrees (with the BST 8mm) and with a Barlow, its only half that much. Jupiter may look like an Orange in the FoV, but quite blurred. The stock barlow that came with your telescope is most likely a single lens, (may not be achromatic) and worst of all, may not have more than a single layer of anti reflection coating.

Therefore, my advice is, get a good barlow, but even better wuld be to invest in an expensive eyepiece for planetary viewing. Try the Fujiyama Orthoscopics available at Lyra Optic, they are made in Japan, are genuine Ortho design, which are excellent for planetary viewing, and cost about £80 each.

Hope this helps.

[Stargazer_00]

Just to provide further context, I was looking at Saturn last night with a 14" reflector and I couldn't even see the Casini division. All I could see was a disc and the rings and even that was wobbly and grainy. It's in such a poor position it's pointless really expecting anything from it for the rest of the short time it has in this rotation.

[AlexB67]

All of the above, I would add, Your BST 8mm and the scope I think has focal length 1200 mm, therefore with a 2x Barlow you magnification will be

300x, even when the planet is a bit higher up that will be pushing it in the UK in most places, unless you have very good skies. Using the eyepiece by itself at 150x it should start becoming a more doable.

To test the collimation quickly, the next time you have a good clear night next, point the scope up near zenith and pick a nice bright star, and do the in and out of focus star test to check if collimation is good or bad. You can use the diagrams on astrobaby's article to see what a star should look like in and out of focus, this will give you a reasonable idea to see if your collimation is poor.

http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

Your scope is almost f/6, so it should be a little more mildly forgiving on collimation accuracy anyway.