Viewing planets with dobsonian

[mental4astro (Alexander)]

You must be wriggling something horrid waiting for your package, hulloleeds, .

Do yourself & your scope a favour & get to a dark sky site to giv the EPs a fang when you can. You are really, really in for a treat.

High power views can be a hit and miss affair. A steady atmosphere is always a lottery to get. It might seem steady down where we are, but up high can be another story. Good luck. To let you know, seeing last night in Sydney was aweful at 11pm. Jupiter was up high, but couldn't get a steady clear view. I was using my 17.5" too, which three weeks ago blew my socks of with views of Jupiter.

By the way, the telescope gods must be smiling on you mate, to not damage the finder, , . You won't be doing that again any time soon.

[hulloleeds]

Hah, yes, the gods were good to me, last night. It wasn't all average - I mean, sitting there observing even a substandard jupiter was quite picturesque in itself.

I'll take a quick look tonight, quite enjoy the crisp air.

[hulloleeds]

So, the EPs came (4 and 15mm superplossl and 42mm superview), Unfortunately I've only really the moon and jupiter to play with so judgement is not based on enough data. The "build quality" certainly is up, compared to the skywatcher included EP's and the 15mm, I quite like, at the moon.

Having said that, I'm continually sort of bummed by lack of detail / size on jupiter. I mean, you can really see the atmospheric turbulence through the 4mm (which was as you might imagine, "fun" to get pointed right ), barely a moment's pure focus before it was all "humid" again. But.. the main thing really being that aside from faint browish stripes, no detail. Is it currently too bright? It does seem plausible that it is simply too bright to hope for detail, but am I expecting too much?, is being in the middle of brisbane (not far from city centre) killing me?

Don't get me wrong, had great fun and I think the EP's will come into their own when I'm trying to look at more than a couple of things. Needless to say, I'm plotting a journey out to darker skies this weekend. However, I'm just looking for someone to maybe point out what my expectations should be.

[erick (Eric)]

See what others say, but if you get in 15 or so nights observing Jupiter, I reckon only 2 or 3 might have good enough seeing for detailed views.

That said, check that you are not observing across metal roofs, expanses of bitumen or car parks. Could be some local thermals in the air due to these areas - particularly, of course, in early summer evenings.

You could try popping your Moon filter onto the eyepiece and experiment. Some feel that reducing the brightness can help?

[hulloleeds]

Thanks for that information Eric, I don't own a moon filter, but I certainly feel that it wouldn't go astray.

It wasn't super high at the time, so I will try tomorrow night.

I wouldn't say that there were any local thermals due to the causes you mention, however I assume that a $29 4mm GSO superplossl is likely to be extremely susceptable to "anything" in the atmosphere?

My basic opinion is that the view was "bright", regardless of eyepiece. Whilst I saw less of the humidity type distortion in less magnified views, I never felt like I was gaining any better detail. I mean, essentially, I could look at it through a 25mm and see the same thing.

Could collimation be required, could that be a root cause?

[mental4astro (Alexander)]

I second what Erick has said. Steady seeing is a lottery. This year so far, I've viewed Jupiter about eight times, only once would I say seeing was steady to really see detail.

There is another trick for newtonians to reduce glare. You can cut some stiff cardboard to a diameter smaller than the scope & place the 'mask' over the opening of the scope. This effectively stops down the scope, just like making the diaphram of a camera smaller. This is usually done on larger scopes, but no reason to not give it a go. Start with a 50% reduction of diameter. You can always cut it larger.

Hulloleeds, you can still have a shot at Omega Centuri & the Carina nebula while the moon is up now, then you can compare them under new moon conditions. Both will stand up pretty well to being pushed from low magnification to high. Really striking.

[hulloleeds]

Thanks mate, I'll try that out.

[PCH (Paul)]

Originally Posted by hulloleeds

Thanks for that information Eric, I don't own a moon filter, but I certainly feel that it wouldn't go astray.

It wasn't super high at the time, so I will try tomorrow night.

I wouldn't say that there were any local thermals due to the causes you mention, however I assume that a $29 4mm GSO superplossl is likely to be extremely susceptable to "anything" in the atmosphere?

My basic opinion is that the view was "bright", regardless of eyepiece. Whilst I saw less of the humidity type distortion in less magnified views, I never felt like I was gaining any better detail. I mean, essentially, I could look at it through a 25mm and see the same thing.

Could collimation be required, could that be a root cause?

Hi HL,

you'll need one sooner or later - a collimator of some sort that is. There's really no way anyone can comment on your collimation as a cause of lack of clarity until you've checked it out.

Laser collimators are cheap enough from the likes of Bintel or Andrews etc. Get one and make sure your coll is set correctly. At the very least, it will allow you to move ahead with your ep collection once you know your collimation is correct.

Also, have you left your scope out for an hour or so prior to viewing - that will help ensure it's at ambient temp, and this will help with the view also.

I moved up to Televue Plossls at about $150 each as my next step up from the cheapo things that are supplied with these scopes. Your choice of a good quality ep will definitely enhance your viewing pleasure. When you feel you have a bob or two to spare, I recommend a pair of Stellarvue Binoviewers from SDM. The view of Jupe thru these will blow your socks off.

Hope this helps

[hulloleeds]

I realise this is somewhat impatient, but my feeling is that this happens to be the moment when I can upgrade my scope, guilt free. I know, a week after receiving my 8 I'm already plotting upgrade . Basically I found out I'm getting tax back, which I wasn't expecting. So, with that in mind, I believe I'm going to get a GSO 12 and sell the Skywatcher.

Not saying that I'm disappointed with the scope, only a fool would make judgements on that regard, I just know I'm in this for the long run and that I won't have an opportunity to reevaluate for quite some time after this so it is either do something now, or don't for another year.

[mental4astro (Alexander)]

Hi HL,

Your upgrade is one of the worst cases of apeture fever I've ever seen! Man, one week!

Just keep in mind, a 12"er is much bigger than an 8". You would need to hitch a trailer to your Charade to tranport it!.

Mental.

[hulloleeds]

Hah, guilty as charged. To be honest I originally planned to get a 12, it's just that the wallet was not actually equipped for such a plan until now.

You don't think the tube will fit across the back seat?

I definitely won't buy a scope that I can't fit in the car

[erick (Eric)]

Originally Posted by hulloleeds

Hah, guilty as charged. To be honest I originally planned to get a 12, it's just that the wallet was not actually equipped for such a plan until now.

You don't think the tube will fit across the back seat?

I definitely won't buy a scope that I can't fit in the car

Put your money in the bank and wait for the AUD to rise further - your buying power will go up.

Learn a lot more with the 8". Much easier to learn on an 8" then on a 12" - I know.

In my Falcon, I would have to remove one rear internal door trim to fit the tube across the seat. You could buy a Hummer?

A 4mm GSO plossl? Paperweight value only, I think. I found the eye relief in the 6mm too small so you must have your eye jammed against the eyepiece?

Yes, the Televue plossls or Vixen LV (better eye relief) - try the second hand market - put out a "Wanted".

Sounds like you were observing Jupiter too low. It is at opposition on 15th so is directly overhead around midnight. However, with a dobsonian mount, it is a struggle to observe at 90 deg elevation, until you learn some tricks (1. - grab the dob base with your spare hand to rotate in Azi. 2. - prop the base base up on one side so the base points to 70-75 deg elevation). Anywhere above about 70 deg should reduce the air column you are looking through.

Your dob may already have an end cover with a reduced aperture hole. Is there a 5-7cm cap that pulls off to leave a hole? Try that - just move the hole to where it isn't over an arm of the spider.

And you have to check that collimation!

[mental4astro (Alexander)]

HL, since you're wanting to get to a dark sky, why not make it to a local star party (check the forum here in IIS, or the club directory in the 'Resources' heading at left). This way you will see many different scope, how big they are & how they perform, before you drop the big bucks.

But do learn on the 8" first, as Erick said. It is an easier scope to handle than a 12".

& if you do get a Hummer, what 12"? 20" dude, .

[hulloleeds]

Originally Posted by erick

Put your money in the bank and wait for the AUD to rise further - your buying power will go up.

Learn a lot more with the 8". Much easier to learn on an 8" then on a 12" - I know.

In my Falcon, I would have to remove one rear internal door trim to fit the tube across the seat. You could buy a Hummer?

A 4mm GSO plossl? Paperweight value only, I think. I found the eye relief in the 6mm too small so you must have your eye jammed against the eyepiece?

Yes, the Televue plossls or Vixen LV (better eye relief) - try the second hand market - put out a "Wanted".

Sounds like you were observing Jupiter too low. It is at opposition on 15th so is directly overhead around midnight. However, with a dobsonian mount, it is a struggle to observe at 90 deg elevation, until you learn some tricks (1. - grab the dob base with your spare hand to rotate in Azi. 2. - prop the base base up on one side so the base points to 70-75 deg elevation). Anywhere above about 70 deg should reduce the air column you are looking through.

Your dob may already have an end cover with a reduced aperture hole. Is there a 5-7cm cap that pulls off to leave a hole? Try that - just move the hole to where it isn't over an arm of the spider.

And you have to check that collimation!

Wait? What is this waiting concept? Free money coming!

I should point out, I wasn't going to drop big bucks, really, by my math I could upgrade for very little outlay - given that I have a brand new skywatcher 8 to sell (that I paid only 500 in the first place for). If I can't get a 12 GSO in my car, though, that might be scuppered as I am not so desperate to part with money for a 10.

I believe I do have an endcover with reduced aperture hole, actually. Now that I think of it. I will try it.

On getting it pointed at 90 degrees, no significant difficulties, I have definitely seen Jupiter when directly above. Didn't help that much, just a bright ball with two faint brown stripes, unfortunately. No real troubles moving the assembly, atall, actually, understandably quite difficult to nail Jupiter in a 4mm eyepiece, but aside from that, I've not suffered too much.

On the eyepiece, I'm sure it would annoy many, but I'm fairly lucky in that sense and I had no significant difficulties looking through it but yes, I'm pretty sure the concept of eye relief doesn't exist, looking through it. It doesn't seem to be an issue with me. Young eyes perhaps?

According to the manual, lack of collimation would show out of focus stars as out of sync decreasingly small circles? I don't really get that, I seem to have centered, as prescribed by the manual, hence, whilst I mention it, as far as I could tell, it wasn't wrong.

Just looking for online hummer store? Anybody got a link?

To me, if I'm already grasping for EP's, it would seem I would be better off first upgrading the base assembly (scope)

EDIT: is it possible that I might need a shroud?

[erick (Eric)]

Originally Posted by hulloleeds

.........

It doesn't seem to be an issue with me. Young eyes perhaps?

.........

To me, if I'm already grasping for EP's, it would seem I would be better off first upgrading the base assembly (scope)

Envious!

I would suggest going for improved eyepieces in the 8" first. They will transfer from an 8" f6 to a 12" f5 quite well.

[hulloleeds]

Originally Posted by erick

Envious!

I would suggest going for improved eyepieces in the 8" first. They will transfer from and 8" f6 to a 12" f5 quite well.

Fortunately, above all, I have X weeks to wait before cash bonanza hits, in this time, I will have at the very least observed through a 10 inch dob. In which case I should have "some" perspective on whether I'm being unreasonable in demanding a better view.

I will continue to try all avenues, to learn more about the issue, of course.

[Paddy (Patrick)]

Originally Posted by hulloleeds

Thanks for that information Eric, I don't own a moon filter, but I certainly feel that it wouldn't go astray.

It wasn't super high at the time, so I will try tomorrow night.

This will be perhaps the biggest issue. Using a 4mm ep in a 1200 mm fl scope means your mag is 300x which generally requires very good seeing. You will get that at the zenith rather than low on the horizon as you are at present looking through a lot of atmosphere. Certainly a good idea to try again when the planet is higher. No scope or eyepiece will give you a good view at this mag with low altitude.

[Jeeps (Sam)]

I've never used a dob, but i'm thinking about getting one. How hard are they to make small adjustments/bumps when tracking/re-aligning an object? I'm a bit worried that if i get a dob i'll have trouble lining things up and wish i had gotten an EQ mount. Maybe i'm just too used to the unstable cheap alt./az scope i've been using

cheers

[hulloleeds]

Originally Posted by Paddy

This will be perhaps the biggest issue. Using a 4mm ep in a 1200 mm fl scope means your mag is 300x which generally requires very good seeing. You will get that at the zenith rather than low on the horizon as you are at present looking through a lot of atmosphere. Certainly a good idea to try again when the planet is higher. No scope or eyepiece will give you a good view at this mag with low altitude.

Oh, it didn't look any different in the 10, 15, or 25 mm EP's either (in terms of detail). 4mm was just an extreme example of how blowing it up revealed no more details.

[hulloleeds]

Originally Posted by Jeeps

I've never used a dob, but i'm thinking about getting one. How hard are they to make small adjustments/bumps when tracking/re-aligning an object? I'm a bit worried that if i get a dob i'll have trouble lining things up and wish i had gotten an EQ mount. Maybe i'm just too used to the unstable cheap alt./az scope i've been using

cheers

It's fairly "hands on". I can't see why you'd find it that difficult, after a bit of practice.

For me, certainly not even on any list of concerns about buying a dob.