Mars ?

[Dazraz]

Hi just went out with my 8" Dob to look at mars and i could see a slight red glow around it but it kept going all blurry plus i could not see the polar cap - will i be able to see the polar cap with a 8" Dob and is this not a good time to be viewing mars ?

I would say that mars through my 7.5mm plossl is the same size as jupiter through my 17mm plossl would this be about right ?

Regards Daren

[Wurzil]

Where I live (north Kent) the air wasnt very stable tonight. Even at 100x Jupiter was "boiling" for me worse than Ive ever seen it. Maybe you had the same seeing conditions where you are. Mars will get closer (and brighter) until 27/01/10, so hopefully you'll get a nice clear, stable sky in the next few months so you can push the magnification up.

Ive heard 150-200x is needed to see surface detail.

good luck

Warren

[Dazraz]

Where I live (north Kent) the air wasnt very stable tonight. Even at 100x Jupiter was "boiling" for me worse than Ive ever seen it. Maybe you had the same seeing conditions where you are. Mars will get closer (and brighter) until 27/01/10, so hopefully you'll get a nice clear, stable sky in the next few months so you can push the magnification up.

Ive heard 150-200x is needed to see surface detail.

good luck

Warren

Probably a silly question but how do i push magnification up the only eyepieces i have are 7.5mm and 17 mm plossl ?

[Wurzil]

Magnification is given as the focal length of your scope (the dob is 1200mm) divided by the focal length of the eyepiece. So the 7.5mm gives you 160x and the 17mm gives you about 70x.

It says on your signature that you have a 10mm plossl (which will give you 120x) and a barlow (which doubles mag) as well??

The maximum "clean" magnification (before you start losing detail) for your scope is about 240x - the 10mm plossl and 2xbarlow will get you exactly 240x - but you will need a very very good clear night to use it without mars wobbling away.

Im just learning all this stuff myself at the mo - it feels good to pass it on!!

good luck

warren

[Dazraz]

Magnification is given as the focal length of your scope (the dob is 1200mm) divided by the focal length of the eyepiece. So the 7.5mm gives you 160x and the 17mm gives you about 70x.

It says on your signature that you have a 10mm plossl (which will give you 120x) and a barlow (which doubles mag) as well??

The maximum "clean" magnification (before you start losing detail) for your scope is about 240x - the 10mm plossl and 2xbarlow will get you exactly 240x - but you will need a very very good clear night to use it without mars wobbling away.

Im just learning all this stuff myself at the mo - it feels good to pass it on!!

good luck

warren

That explains it clearly many thanks for that. It seems to be getting more clear outside im off for another look he he !

[John]

I could see the pole cap with my 5" refractor a couple of nights ago but other surface detail was at best only suspected rather than seen clearly.

Your scope is a good one for planets (I've owned one !) but you will find around 200x -250x is the practical limit on most nights because of our UK seeing conditions.

John

[russ]

I wouldn't be too worried about what you saw. The evening (anything upto 1am) view of Mars is quite poor. But your scope is more than upto the job for a good view of Mars.

It's best to observe Mars in the morning for the moment. The evening view should improve greatly over the next month or so.

Stick with it, you'll get a good look at the red planet soon.

[ashenlight]

Russ is right Daz, get out there in the morning and you'll get a better, more stable view. Observe for as long as you can, that way the seeing has more chance of stabilizing and you might get a fleeting few seconds of the most amazing view - you've just gotta stick with it.

Good luck

[dweller25]

I have the same scope as you and used x300 to view Mars on the 4th Dec - and it was still small !!

It is definitely best viewed in the morning when the air is steadier.

Here is what it looked like.......

[Dazraz]

I have the same scope as you and used x300 to view Mars on the 4th Dec - and it was still small !!

It is definitely best viewed in the morning when the air is steadier.

Here is what it looked like.......

What did you use to get to 300x ?

[dweller25]

I used a Televue 8mm Plossl and a Celestron x2 Ultima barlow.

Your 7.5mm Plossl will give x320 with your x2 barlow.

To get a good view of Mars requires :-

1. Scope fully cooled.

2. Scope well collimated.

3. Good seeing.

4. At least x200.

5. A clear sky - this one is a bit optimistic !!!!

[russ]

To get a good view of Mars requires :-

1. Scope fully cooled.

2. Scope well collimated.

3. Good seeing.

4. At least x200.

5. A clear sky - this one is a bit optimistic !!!!

Perfect advice

You should find the detail showing at around 200x. At the moment a morning viewing session is essential to nail points 3 and 4. The weather is looking promising for tomorrow morning down this way, hopefully that maybe the same elsewhere.

[Dazraz]

I used a Televue 8mm Plossl and a Celestron x2 Ultima barlow.

Your 7.5mm Plossl will give x320 with your x2 barlow.

To get a good view of Mars requires :-

1. Scope fully cooled.

2. Scope well collimated.

3. Good seeing.

4. At least x200.

5. A clear sky - this one is a bit optimistic !!!!

Hi ok i havn't ventured in to collimation yet but if i get a crystal view of the moon then i assume my scope is collimated yes ?

[pvaz]

Not really. The moon handles bad collimation, you should check it. My scope is the same as yours and it gets a bit out of collimation every 3 weeks or so due to small bumps, I think.

I only managed to see the polar cap at 6 am when Mars is really high. I used a 5mm EP and a 9mm EP on a scope with same aperture and focal length as yours. Your 7.5mm should be fine but Mars is indeed small and you need a steady night.

That dawn was particularly steady and both Mars and Saturn ware very stable.

[dweller25]

You need very good collimation for the best planetary views.

You should point your scope at a star and slightly defocus. You will then see lots of concentric rings, if the rings are shifted slightly off to one side you need to collimate. It's not hard to do and it's a two minute job if someone can help you.

[russ]

There's very simple newtonian collimation tutorials around, including an excellent one by one of our SGL members:

Astro Babys Guide to Collimation

You can do a simple star test to check collimation is good. The moon can look good even if the collimation is slightly off.

[Dazraz]

ok i will do a star test tonight - i will say though that i am really worried about collimation as everything i seem to touch breaks

[pvaz]

Just be calm about it and take your time. The 1st time I did it I toke like half an hour and did it 3 times. I started to align the secondary when it was almost perfect and I did worst.

Then I toke my time and done it right.

Now it's a 5min job when alone and I don't have a laser collimator that speeds things up.

Read the guide carefully, watch the video too. Then do it.

Only a few important things to remember:

1) The secondary rarely gets misaligned. If it is, adjust it with the scope in an horizontal position. In case you completely loosen it up, witch is very hard to do, it won't fall over the primary.

2) don't touch the face of the secondary with your fingers, only the back.

[russ]

1) The secondary rarely gets misaligned. If it is, adjust it with the scope in an horizontal position. In case you completely loosen it up, witch is very hard to do, it won't fall over the primary.

Or you drop the allen key down the tube.......gulp.

At this stage don't touch the secondary mirror, just see how the primary is doing with the star test.

[TheThing]

Try this video for collimating - very clear and concise.

With regards to Mars, it can be a good sight in the evenings too, so don't write them off. I was able to see the North polar cap very clearly at about 10:30pm on the 1st with my 4" Mak.

[russ]

With regards to Mars, it can be a good sight in the evenings too, so don't write them off. I was able to see the North polar cap very clearly at about 10:30pm on the 1st with my 4" Mak.

You are absolutely right Hugh. Always worth checking at every chance, you just never know. Had some cracking views of Jupiter this year despite its low elevation.

[TheThing]

It's sometimes just down to luck and good seeing!

Tha same night Mars was clear, jupiter was lost behind thick cloud. You can't win 'em all!

[Darth Takahashi]

I don't want to put you off but Mars is a really tough planet to observe and image. Mars is half the size of the earth and 2.3 AU distance, therefore, its a very small object in the night sky, hence the magnification needs to be 150x - 250x and upwards.

Truth me when I tell you that our Northern European weather conditions rarely support the necessary magnification to see detail on Mars. You need a really stable and transparent night, not impossible, just rare.

I myself have never given Mars much time and effort because of these issues.

P.S. You can't check collimation against extended objects like the Moon, you can only check it with a point source such as a star. Make sure you use one close to the zenith (over head) less atmosphere to disturb the star and make sure its not too bright either etc...

Neil.

[Dazraz]

Has anyone got a link to buy a collimation cap ?

[russ]

Here's a link to the First Light collimation page:

Collimation