Is my scope meeting its potential?

[cpgolda]

Hello everyone,

For several years I’ve enjoyed astronomy through television and magazines, but now my kids are getting to the age where they can enjoy it as well, so I finally decided to take the plunge and buy a telescope in hopes of bringing our learning experience alive a little more. Trying to avoid upgrading sometime down the road, I decided to go fairly large right from the start and bought a Celestron 8 inch Schmidt Cassegrain (as a newbie, I probably should have started smaller).

So far, I’ve been partially happy with my views (Saturn is pretty nice, I can somewhat make out the bands on Jupiter, and the moon is simply amazing in detail) but honestly, I’m having this nagging feeling that either I am doing something wrong or my OTA is somehow not optimized for viewing. Mostly, this is due to the fact that I can barely make out the bands of Jupiter and when I look at MARS (without filters) all I get is a shiny white ball. While I chalked the view of Jupiter up to variables like time of year, city light, and the fact that my mount is on my back deck (which doesn't provide the greatest stability), the situation with MARS concerns me more. I even went out a day after MARS opposition, thinking that maybe my initial (poor) observations from a few months prior might have had something to do with distance, but at this time (4 March 2012 @ 8:30 from Maryland) it was at a good angle in the sky (which I hoped would have given me more of the longer red wavelengths) and pretty much as close as it’s gonna get for a while (.65 au or so ??). At this time, all I was able to bring into focus was a slightly larger shiny white ball (through strangely enough it was still red when viewing with my eyes).

Does anyone know if this is an expected result or is there something I’m doing wrong?

I thought collimation might be an issue, but if this was so, wouldn’t I have problems with my other views of Saturn and the moon?

Is it possible I'm getting too much light and I somehow need to attenuate it with a filter?

Not sure if this will help, but my viewing was with a 25mm and 13mm eyepiece.

Thanks so much for any help you guys can provide. I’m pretty much all out of ideas and don't really know what I'm doing, so anything would be greatly appreciated.

Sincerely,

Chris

[umadog]

Have you star-tested it?

[glowjet]

Mars is always a difficult target and often brings disappointment visually, unless the seeing is good to perfect, if you are happy that your scope is spot on in collimation, though it is always good to run some periodic checks, then perhaps you could consider using a filter, I can`t remember which is suitable, but I am sure someone will advise before long

[coulthamst]

Hi cpgolda. I live in a city - naked eye visibility 4.1 at best - and had the same difficulty as you. I find that a ND25 filter reduces the brightness sufficiently to see the polar cap and some indication of dark markings. ND filters are sold as "Neutral Density" or "Moon Filters".

Hope this helps

Jim.

[kniclander]

the bands on jupiter should be very obvious through pretty much any size scope (with SEB ditinctly wider than NEB) and whilst mars is difficult, the polar ice cap and some of the dark features should be visible. If it's not collimation it could be dew or could well be vibrations from your deck.

[Carbon Brush]

Hi. A good quality scope will provide much better images than the sky will allow on most nights. In other words, the sky is the limiting factor, rather than the scope.

So most nights Mars will be a uniform blob. One night in ten, the sky will be good enough to show detail. This means you just have to be patient. Use the time to address known weaknesses in your setup. The bouncy floor is an obvious one.

As an example of viewing. A week or so ago I was viewing Mars with a TAL200K. It was a disc with only a vague hint of detail. Using a skyglow/nebula filter, I clearly saw a polar cap. Using a red filter the main surface features jumped into view. Last night Mars was a blob. But it was obvious that there was no point in trying harder. Looking at the moon showed just how turbulent the air was. So my decent scope performed, on the night, no better than a £50 scope. But next week?

[BlueAstra]

I don't have the reference, but you can get a mask to fit on the front of the SCT to aid collimation adjustment ( looks a bit like the radiation warning symbol). Produces 3 lines from a star target that you use the collimation screws to align so that the tips touch. Also filters will help with contrast to see features.

[Gomtuu]

I feel your pain

I live in the centre of a city and could only just make out the bands on Jupiter last night even though my collimation looked pretty good. The combination of light pollution, average quality EP and some serious shimmering was what I put it down to.

Maybe when I get out to a dark site (jog on clouds!) I'll get a better idea of what mine can do.

[mike.brightmore]

Planets are fickle targets because they are so susceptible to atmospheric conditions. Splitting double stars is a good test of optics. There are plenty in Orion or you could have a look at Castor in Gemini.

[cpgolda]

Thanks for the tip. I honestly haven't tried that. When I first bought my telescope a few months ago, I think I assumed that everything was fine because the views of the moon were so spectacular. I guess I figured that collimation issues and stuff would be more evident (you either had a good view or a terrible view), but now I'm starting to see it as as being more on a spectrum, which means that maybe the views that I think are so great could be much better.

Anyway, I'll definitely start researching the star testing. In my initial research on the topic, I kept running into a book authored by Harold Suiter. It looks like it might have some answers, though I must admit, it looks to be a daunting task....

Thanks again for the tips.

[cpgolda]

Have you star-tested it?

Thanks for the tip. I honestly haven't tried that. When I first bought my telescope a few months ago, I think I assumed that everything was fine because the views of the moon were so spectacular. I guess I figured that collimation issues and stuff would be more evident (you either had a good view or a terrible view), but now I'm starting to see it as as being more on a spectrum, which means that maybe the views that I think are so great could be much better.

Anyway, I'll definitely start researching the star testing. In my initial research on the topic, I kept running into a book authored by Harold Suiter. It looks like it might have some answers, though I must admit, it looks to be a daunting task....

Thanks again for the tips.

[cpgolda]

Have you star-tested it?

Thanks for the tip. I honestly haven't tried that. When I first bought my telescope a few months ago, I think I assumed that everything was fine because the views of the moon were so spectacular. I guess I figured that collimation issues and stuff would be more evident (you either had a good view or a terrible view), but now I'm starting to see it as as being more on a spectrum, which means that maybe the views that I think are so great could be much better.

Anyway, I'll definitely start researching the star testing. In my initial research on the topic, I kept running into a book authored by Harold Suiter. It looks like it might have some answers, though I must admit, it looks to be a daunting task....

Thanks again for the tips.

[cpgolda]

Mars is always a difficult target and often brings disappointment visually, unless the seeing is good to perfect, if you are happy that your scope is spot on in collimation, though it is always good to run some periodic checks, then perhaps you could consider using a filter, I can`t remember which is suitable, but I am sure someone will advise before long

Thanks for the help. That makes me feel a little better, and perhaps the scope isn't as "off" as I originally thought. Though I'm still curious, shouldn't MARS still be red through a scope? I just can't figure it out.

[cpgolda]

Hi cpgolda. I live in a city - naked eye visibility 4.1 at best - and had the same difficulty as you. I find that a ND25 filter reduces the brightness sufficiently to see the polar cap and some indication of dark markings. ND filters are sold as "Neutral Density" or "Moon Filters".

Hope this helps

Jim.

Ahh, yes...great idea. I forgot about the moon filter that came with my celestron setup. I'll give that a try next time I'm out there. Thanks for the help.

[Capricorn]

I am actually a bit concerned. Mainly owing to your descriptions of Saturn and Jupiter.

You say that for Jupiter

I can somewhat make out the bands on Jupiter,

I can make out distinct sharp bands on Jupiter using a short 70mm refractor at 30x. Agreed it is small but it is sharp and distinct. The 4 moons also show their individual colours - just dots but obviously different.

For an 8" SCT to make you say you can somewhat make out the bands isn't what I would expect.

Saturn should be brilliant not

Saturn is pretty nice

Mars I would sort of forget, every year I read of people trying Mars and failing to get anything distinct. Then one person in about 8 or 10 manages to get a clear view and everyone tries again. I think a fair bit of luck is required with Mars.

You do not say the eyepieces that you use, nor the time of viewing, Jupiter gets low fairly early and this will degrade the view. With an 8" I would suggest something like 100x for Jupiter. It is bright enough to swamp a small image with light. So possibly making the banding indistinct. For Saturn 120x to 150x.

As most SCT's are about f/10 that makes it something like a 20mm eyepiece and something like a 15mm. The 15mm could be good for both Jupiter and Saturn looking at the numbers.

If you really wanted to try Mars then a reasonable 8mm eyepiece, and some luck.

[Stu]

Cool down time is also important for your type of scope, how long are you leaving it out before using? My mak can take 1.5 hours to cool if taken out from indoors, then it will give great images. I believe Cassegrains need less because the front plate is thinner but it will still need plenty of time.

The moon is a bit of a red herring really because it tends to look pretty amazing through anything and takes high magnification quite easily.

Mars is very tricky, and variable. I have had very good, and quite rubbish sessions on it. Sometimes lots of detail, others literally none.

I do think larger scopes tend to be more sensitive to seeing, particularly at longer focal lengths and for planetary use. Smaller refractors can often cut through poorer seeing better. As per previous poster, I can see clear bands on jupiter, plus GRS and shadow transits when they occur, with a 66mm apo doublet refractor.

In summary..... Leave it out to cool for a decent amount before using. Star test it and collimate it if it needs it. Try on a number of different nights to get good seeing, and avoid observing over houses if possible. Provided it stays clear, things often look much better as they get higher, and as the atmosphere cools and stabilises in the early hours. Lastly, be patient at the eyepiece, it takes a while to get your trained to see the detail, and there will be moments of very good seeing when the detail suddenly snaps into focus. That reminds me, don't chase the focus, get it right, then leave it and wait for the seeing to clear.

Enough rambling, hope that is of some help

Good luck

Stu

[LukeSkywatcher]

Good point Stu. I was just wondering why no one else had mentioned the cooling down of the scope. This would most likely be the cause of the planets appearing as white circles. Ive experienced it myself with the 8SE.

Mars is fickle. Dont give up on it. I had really good views a couple of nights ago.

Basically, leave the scope outside to cool down for an hour even longer if possible. It makes a hell of a difference.

P.S.~~~you will need a dew shield with the SCT. They mist up pretty quickly.

[rory]

thats an exellent scope you have, im sure it will perform well,patience and practice is what i keep being told.

i think cool down takes a fair while with sct's.

[Moonshane]

I agree the most likely cause of problems with this sort of scope is inadequate cooling. I bet if you cool it as suggested by Stu the images will be a lot better. sky based light pollution has no effect on planets/moon and can in fact enhance the view - sometimes more detail can be seen on planets when the sky is still a bit blue.

direct light from kitchens etc can impact a lot though. that said, I find a Baader Neodymium filter really generally enhances the view of planets and moon.

wait until Mars is high in the sky too this will reduce atmospheric effects. your scope is a very capable planetary and general observing scope.

[Peter Drew]

I use a Celestron 8SE, I find that something like a 13mm eyepiece is far too low a magnification for a good view of Mars. A 8mm, 7mm or 6mm should be a lot better provided that the scope is well collimated, cooled and the seeing conditions are good.

[mt01]

do you have and use a dew sheild ??

[cpgolda]

Hi everyone,

I just wanted to say thank you to everyone that has helped me out in this thread. This is first time I’ve been on this forum and I was so happy to find that so many people out there are willing to take the time to provide their insight and share their experiences.

I’m still having some difficulties with the nuances of how forums work (my individual responses don’t seem to get posted where I expected ), but once I get it all worked out, I’d like to provide individual responses when I can. In the meantime, let me just say that all the replies here have been very helpful in many different ways; some have helped me to gauge what I should be seeing with my telescope, some have helped me to ease the frustration of having unrealistic expectations, and others have given me a good sense of the variables I should concern myself with when trying to get optimal viewing performance.

Thanks again…I’ll post my results back here as I try out all the different suggestions.

Sincerely,

Chris

[cpgolda]

the bands on jupiter should be very obvious through pretty much any size scope (with SEB ditinctly wider than NEB) and whilst mars is difficult, the polar ice cap and some of the dark features should be visible. If it's not collimation it could be dew or could well be vibrations from your deck.

Yeah, I'm starting to think that the deck might be one of the many issues. Unfortunately, the trees in our backyard that we originally appreciated for giving us some privacy really have become an annoyance when it comes to astronomy, as they pretty much block a large portion of the sky. The back deck is high enough to give me a fair view, though it obviously has its own issues. Thanks for the help on narrowing things down a bit.

[cpgolda]

I am actually a bit concerned. Mainly owing to your descriptions of Saturn and Jupiter.

You say that for Jupiter

I can make out distinct sharp bands on Jupiter using a short 70mm refractor at 30x. Agreed it is small but it is sharp and distinct. The 4 moons also show their individual colours - just dots but obviously different.

For an 8" SCT to make you say you can somewhat make out the bands isn't what I would expect.

Saturn should be brilliant not

Mars I would sort of forget, every year I read of people trying Mars and failing to get anything distinct. Then one person in about 8 or 10 manages to get a clear view and everyone tries again. I think a fair bit of luck is required with Mars.

You do not say the eyepieces that you use, nor the time of viewing, Jupiter gets low fairly early and this will degrade the view. With an 8" I would suggest something like 100x for Jupiter. It is bright enough to swamp a small image with light. So possibly making the banding indistinct. For Saturn 120x to 150x.

As most SCT's are about f/10 that makes it something like a 20mm eyepiece and something like a 15mm. The 15mm could be good for both Jupiter and Saturn looking at the numbers.

If you really wanted to try Mars then a reasonable 8mm eyepiece, and some luck.

Thanks for all the help. I will definitely use the recommendations on the eyepieces. Originally, I know I was using a 25mm and I think the other was like 13mm or so for viewing Saturn and Jupiter.

Yeah, your description of Jupiter doesn't quite match what I'm seeing, which concerns me a bit. When viewing Io, Europa, Ganymeade, Callisto, I simply get 4 bright white dots. I never guessed you would be able to get differences in color.

As far as Jupiter itself goes, I think two out of the last four times I could see the bands in what I would describe as fairly cleary, but they were not as sharp as I expected. A third time they were somewhat faint. The last time, they were not visible at all; Jupiter was pretty much a washed out white ball. I have to admit though, part of this may be due to external factors that I did not consider. For example, I believe my neighbor's and my house's lights were still on (which was visible from my observing spot), Jupiter was already starting to set, and I don't think I left much time for temperature eqilibrium. I think these may have contributed, but still, I don't think that they account for the complete picture.

Due to all the potential variables, this is kind of hard to guage, but on a fair day, what should I expect to see from Saturn with an 8" SCT, using a 13mm or 25mm around this time of year? My last obervation was about a month or two ago at around 1:00 am, so it was still really low in the east. I was able to get a crisp view of the planet, along with the rings, but I think that was about it. I couldn't make out the Cassini division or anything like that, and definitely didn't get any color (though I'm not sure if either of those are possibilities).

Thanks again for the help.

[cpgolda]

Hi. A good quality scope will provide much better images than the sky will allow on most nights. In other words, the sky is the limiting factor, rather than the scope.

So most nights Mars will be a uniform blob. One night in ten, the sky will be good enough to show detail. This means you just have to be patient. Use the time to address known weaknesses in your setup. The bouncy floor is an obvious one.

As an example of viewing. A week or so ago I was viewing Mars with a TAL200K. It was a disc with only a vague hint of detail. Using a skyglow/nebula filter, I clearly saw a polar cap. Using a red filter the main surface features jumped into view. Last night Mars was a blob. But it was obvious that there was no point in trying harder. Looking at the moon showed just how turbulent the air was. So my decent scope performed, on the night, no better than a £50 scope. But next week?

Thanks for the much appreciated information. I was really getting frustrated with the view of Mars I was getting. Though I haven't ruled out the need for telescope adjustments just yet, I do think that my expectations for Mars were a little unrealistic before I stopped by this forum. This was very valuable for me to learn because I would have otherwise spent a long time underappreciated my telescope.