Jump to content

Banner.jpg.39bf5bb2e6bf87794d3e2a4b88f26f1b.jpg

StellaLyra 10" Planetary Viewing Question


Recommended Posts

Hello World!

This is my first post in Stargazers Lounge so hello everyone 😊

I recently purchased my second telescope at the end of August which was a StellaLyra 10” dobsonian from FLO and was looking for a bit of advice around planetary viewing.  When looking at Jupiter (or Saturn) with the 9mm Plossl eyepiece that comes supplied with the telescope the planet is just a fuzzy white blob and am not able to make out any detail at all. I can make out some dots, which I believe are the moons but can make out no detail of the planet whatsoever.

I have checked the collimation a few times using the Laser and a Cheshire and it seems to be spot on with the laser being dead centre on the primary mirror and secondary being aligned, so I was looking for some additional advice as to what might be causing the problem.  Interestingly, I don’t seem to have any problems with Deep Sky Objects using the 2” 30mm Super View eyepiece with views of Pleiades and Orion nebula looking truly amazing.  Also, looking at the moon with the 30mm Super View looks crisp and sharp, but when I switch to the 9mm it seems to lose image sharpness. Finally, looking at Betelgeuse as a test I’m not able to get the star down to be a single ‘dot’ with the 9mm, but can do so easily with the 30mm, so it feels to me like a higher magnification problem.

I guess my first question is: Does poor collimation have a greater impact on higher magnification eyepieces or should I expect it with the 30MM eyepiece as well?  Is this most likely to be a collimation problem or is there something else I need to check?

As an aside, in the other research that I have done on the subject suggested that it might be down to atmospherics/light pollution/unreasonable expectation, but the last time I looked at Jupiter with my old Meade ETX90, I could make out a little detail so thought the StellaLyra would be much better.  I’ve also tried this quite a few times over 3 months now and seem to be getting the same results, so I think I can rule out bad atmosphere.  What I might do next is to bring out my old Meade and set them up side by side to at least rule out environmental issues and maybe swap eyepieces out to rule out the 9mm Plossl..

I would appreciate any advice/guidance anyone can give me on this one..

Rod

P.S. Not a cloud in the Sky tonight, so I’m heading back outside 😊

StellaLyra 254mm (10") optical aperture / 1250mm focal length / f/4.9 focal ratio

Link to comment
Share on other sites

Hi and welcome to SGL.

It is quite possible that your collimation is not spot on. This shows on higher magnification, while views at low power will look ok.

One way to check that would be to insert 9mm eyepiece, turn your scope to Polaris (it is easier if star is not moving) - put it in center and then slightly defocus it both in and out focus.

You should see concentric rings each side of focus - something like this:

image.png.2f1ce75c76e9d5788012bd92b1532ba3.png

In focus / slightly defocused. Notice how things are concentric. If you see something like this:

image.png.30c86620327d5646c5fee35f6ab583a9.png

then your collimation is slightly off and it's blurring your views.

There might be other things as well that impair your viewing - like thermal issues. Is your scope properly cooled down?

How about local thermals - are you observing over rooftops of adjacent houses? They are probably heated this time of the year and that creates turbulence above their roof tops.

There could be just seeing issues - unstable atmosphere as well.

 

  • Like 1
Link to comment
Share on other sites

22 minutes ago, ScotRod said:

but the last time I looked at Jupiter with my old Meade ETX90, I could make out a little detail so thought the StellaLyra would be much better.

Hi from Edinburgh,

Larger apertures suffer more from poor seeing conditions. Your dob catches (250^2*π)/(90^2*π) = 7.7 times more light but also looks through 7.7 times more atmosphere! Smaller scopes can often "punch through" poor seeing than the big guns. However, when the seeing is good, the larger aperture will have significantly higher resolution.

Also - have you tried the 9mm EP in the Meade? It might be a bit dodgy.

Link to comment
Share on other sites

@vlaiv,

The telescope has been outside since 5pm so cooling shouldn't be a problem.  Humidity is low enough, so no dew as far as I can see.  I think there is plenty of clearance on the rooftops, so shouldn't be an issue.  Let me check your suggestion with Polaris and I will drop a note back in here.

@Pixies

That's a fair point on both.  I'll switch the eyepieces round when the sky is clear (hopefully tomorrow) and at least I can rule out the eyepiece.

Thanks both for the prompt reply!

Link to comment
Share on other sites

@vlaiv

I tried your suggestion around coming in and out of focus.  When out of focus, I do indeed get the rings around the star, but when coming into focus it's as if the star has spikey protrusions (not sure if that makes sense?) only at the top.  Any ideas what that might be?

I think that I need to try with my old telescope and maybe switch out eyepieces and see if that makes any difference...

Link to comment
Share on other sites

2 minutes ago, ScotRod said:

Any ideas what that might be?

Does it look like this:

image.png.54b1da1bedca5dc85c0ac3bef8dd93b7.png

when you are near the focus?

That would suggest that your telescope is not properly cooled and you have thermals inside ota.

 

Link to comment
Share on other sites

Owner of the 8" version. Had something a little similar when I was last out, mostly at high mag. Looked clear but turned out the jetstream was having a wild time above and I put it down to that - it could be the same for you, just bad seeing conditions. Stars would seem to come in and out of focus with 9mm but not so much of an issue with lower mag. Wasn't quite as bad as you described but I also haven't tried out the stock 9mm that came with it either. Looking to take it out tonight if the weather stays good as predicted and can give the stock 9mm a try vs 9mm redline I have and see what happens. Jetstream is going to be right above me again too.

Clear outside has all green forecast for me but meteoblue has it down as bad seeing for me tonight.

Edit - duplicate word removed

Edited by Stickotron
Link to comment
Share on other sites

I had some good views of Jupiter and Saturn in my 8” Skyliner in the summer and early part of autumn. 
 

But since then and recently the seeing has been poor to terrible. Not sure why but for me (every time I’ve tried) it’s no where near as good as it was earlier in the year. 

Link to comment
Share on other sites

@vlaivIt's more like just spikes at the top but the nothing at the bottom (when in focus).  Imagine a single star point with those spikes along the top...

@PixiesThat's a great article, thanks.  I'm going to move my telescope to the bottom of my garden just to rule out any heat coming from being too close and any ambient heat causing an problem.

@Cosmic Geoff That's definitely a possibility.  I've hauled out my old Meade, so going to rule out Atmospherics (if I can get some clear skies tonight) by trying a different eyepiece.  Forecast looks good, so fingers crossed.

@Mr Spock The telescope is stored inside, but I usually take it out an hour or two before use and collimate once outside.  I believe that for a 10" telescope 30-60 minutes is sufficient for cooling down (I also have a fan on the primary mirror as well, but not sure what real difference this makes).

@Stickotron Appreciate it.  Let me know how you get on.

@Dave scuttNo, I just have the 1.25 Adapter.  You think it's worth trying with the 2" at the same time (or are you ruling it out)?

I've found my old Meade eyepiece, but it's a 22mm with a 2x Barlow.  I'll give them a try and see how it looks and if it's any better but I think I might buy a decent 8-9mm eyepiece and see if it improves.  I don't think it will be a waste if I do purchase another one as from what I understand, the stock eyepieces aren't usually the best (more just to get you up and running), so even if it does turn out to be atmospherics, still a good investment.

One final note; thank you everyone for taking the time to reply.  All feedback is greatly appreciated!

Clear Skies!

  • Like 1
Link to comment
Share on other sites

Hi ScotRod I have the 8” version of your telescope and I have managed to achieve several decent viewing sessions of the gas giants. First and foremost I was pretty meticulous with the collimation, especially the secondary mirror which required adjustment. Secondly having had nothing but trouble with high power eyepieces that are supplied with telescopes I didn’t use the supplied 9mm , but instead used a BST Starguider 8mm. Whilst I have had several good nights I have also had nights when the seeing just isn’t conducive for planetary viewing. I also use the fan on the primary mirror as an aid to the cool down.

Link to comment
Share on other sites

14 minutes ago, ScotRod said:

It's more like just spikes at the top but the nothing at the bottom (when in focus).  Imagine a single star point with those spikes along the top...

I suspect you might be seeing coma. What happens if you move the position of the star around then field of view? Does the direction of the spike change? For a properly collimated scope there should be no tail when the star is precisely centered, with the tail pointing away from the center when the star is not centered. If you find that the tail directions all point away from a star position that is not in the centre of the field of view you need to recollimate your scope. 

Link to comment
Share on other sites

@ScotRod had a quick viewing session this evening. Work in the morning. Allowed scope to cool for an hour and half. Checked out jupiter and x4 moons initially with a 20mm, looked nice, could see bands but not the greatest view. Switched to 9mm redline, looked OK, in and out of focus, shimmering style effect on it. Made it hard to pick out details, sometimes to the point where it looked like a fuzzy white blob for a few seconds but also could see banding at times.  I believe this is bad seeing due to turbulence in the air. Switched to stock 9mm and same effect, slightly worse image but not that bad in comparison to the redline 9mm I own, just a more difficult to use eye piece with a smaller view. 

I don't recall jupiter being like that the first couple of times I used the scope as it was a lot more stable image. However, Jupiter is now currently above a neighbours house which I'd imagine doesn't help the image due to rising heat.

Switched over to the moon since it'd appeared behind me, views fantastic in the 2inch stock 30mm. Tried 20mm redline, the same. Switched to redline 9mm and view was still crisp but slightly shimmering on the edges of the moon, switched to stock 9mm and very similar performance to the redline with the shimmering in the edges, again just didn't feel as comfortable to use and smaller view.

Is it possible that you're just having bad seeing? Just my guess.

Can't comment on your defocus star test issues and I'm an inexperienced telescope user so I'm sure others would be able to help a lot more with that.

Hopefully you get it sorted

Link to comment
Share on other sites

9 minutes ago, Stickotron said:

@ScotRod had a quick viewing session this evening. Work in the morning. Allowed scope to cool for an hour and half. Checked out jupiter and x4 moons initially with a 20mm, looked nice, could see bands but not the greatest view. Switched to 9mm redline, looked OK, in and out of focus, shimmering style effect on it. Made it hard to pick out details, sometimes to the point where it looked like a fuzzy white blob for a few seconds but also could see banding at times.  I believe this is bad seeing due to turbulence in the air. Switched to stock 9mm and same effect, slightly worse image but not that bad in comparison to the redline 9mm I own, just a more difficult to use eye piece with a smaller view. 

I don't recall jupiter being like that the first couple of times I used the scope as it was a lot more stable image. However, Jupiter is now currently above a neighbours house which I'd imagine doesn't help the image due to rising heat.

Switched over to the moon since it'd appeared behind me, views fantastic in the 2inch stock 30mm. Tried 20mm redline, the same. Switched to redline 9mm and view was still crisp but slightly shimmering on the edges of the moon, switched to stock 9mm and very similar performance to the redline with the shimmering in the edges, again just didn't feel as comfortable to use and smaller view.

Is it possible that you're just having bad seeing? Just my guess.

Can't comment on your defocus star test issues and I'm an inexperienced telescope user so I'm sure others would be able to help a lot more with that.

Hopefully you get it sorted

Are those the redline SVbony you’re using?. I initially did all my observing from my back garden, but being surrounded by neighbors houses on all sides ,I moved to a playing field in a park. This is only about 100 meters from my house so not an issue. I can honestly say that with my telescopes being cooled to ambient and my collimation being checked my planetary viewing has improved. On poor viewing nights I know that it’s the seeing and transparency responsible. I hope you find the problem.

Link to comment
Share on other sites

I observed Jupiter this evening with my 200mm Orion Optics newtonian. Similar results to yours. Last night Jupiter was a lot crisper with my 100mm refractor. I think the current altitude of Jupiter plus the seeing conditions tonight (we have the jetstream over much of the UK tonight) are hindering the views. Last night I suspect the seeing was better plus the refractor seems to cut through turbulence in the atmosphere.

Most of my planetary observing lately of Jupiter and Saturn has been with refractors despite having a couple of nice reflectors of significantly larger aperture. When those planets are better placed (ie: higher in the sky) the additional aperture of the reflectors will give them an advantage. I also observed Uranus tonight, which is a lot higher in the sky than Jupiter, and got a crisply defined view of the small (3.75 arc seconds in apparent diameter) disk of Uranus even at 348x magnification.

Probably nothing amiss with your scope, eyepieces etc, just the positioning of Jupiter (it will be lower still in Edinburgh) and the jetstream.

 

 

 

 

 

 

 

 

 

 

Link to comment
Share on other sites

12 hours ago, bosun21 said:

Are those the redline SVbony you’re using?. I initially did all my observing from my back garden, but being surrounded by neighbors houses on all sides ,I moved to a playing field in a park. This is only about 100 meters from my house so not an issue. I can honestly say that with my telescopes being cooled to ambient and my collimation being checked my planetary viewing has improved. On poor viewing nights I know that it’s the seeing and transparency responsible. I hope you find the problem.

They are not SVbony branded but the same generic line of them as far as I'm aware. The red line 68 wide field view. Managed to pick up the set of 4, 6mm, 9mm.15mm and 20mm for £59 off amazon earlier in the year.  Thought that was a good deal.

Also agree about the jetstream making the seeing appalling. Had that experience on my last two nights out.

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.