Sky-Watcher 200p Dobsonian

[rajanp]

Hi all, firstly I'm a complete beginner and I've just purchased a Sky-Watcher 200p Dobsonian scope. I've gone through the process of collimation following Astro-Baby's guide and the collimation pattern I see through my cheshire looks pretty good now - I'm seeing concentric circles with the centre spot on the Cheshire in the middle of the primary mirror ring. I'm noticing something a bit odd using the 25mm eyepiece that came with the scope however, the image seems to jump around moving my eye from exactly on-axis with the eyepiece to slightly off-axis. Additionally the image isn't hugely sharp but i'm not sure if I'm just expecting too much from a pretty basic eyepiece and scope? Does anyone know if an image appearing to shift around moving when moving your eye line at the eyepiece from on-axis to slightly off indicates that collimation is off or it's an issue with the eyepiece? 

I hope that makes sense and someone might be able to help!

[Jasonb]

Welcome to the forum, it's a very friendly bunch here!

I'll start this by saying I'm a newbie too. But if what you're describing is that the when you move your eye around while looking in the eyepiece, the image in the eyepiece moves as well, then as far as I know that's perfectly normal, and nothing to do with collimation or anything like that.

I know you say you've a pretty basic eyepiece and scope, but while the 25mm that comes with Skywatcher telescopes is considered basic but ok, your 200p Dobsonian I wouldn't call basic at all, that's a great scope and you should be very happy with it! I've a 130p and I love it, and you'll get a lot more light with the 200p.

Enjoy...

[wulfrun]

As said, the scope isn't basic but the eyepieces are considered "starters" and won't be the best. Sounds like you got the collimation spot on and having to get your eye in the right spot is normal.

[Spile]

I think the star test is the simplest, easiest and most accurate way to check collimation.

I follow Gary Seronik’s no-tools collimation advice

https://garyseronik.com/a-beginners-guide-to-collimation

and can recommend the Small Optics guide at

https://www.youtube.com/channel/UCVi6UI5BvXm9lyZg5AG0X1g/videos 

[KP82]

From what you've described, it's perfectly normal. Some eyepieces (not just the basic ones) are less tolerant with the position of the eyes than the others.

With regards to sharpness, the stock 25mm ep while being very basic should provide sharp on-axis views. Off axis views generally suffer from field curvature, coma and astigmatism in these starter eyepieces. Sometimes the quality of the views would also get affected by the seeing condition. BTW there is a central obstruction in the reflectors/catadioptrics design that could reduce the sharpness/contrast slightly. So you can't expect them to produce the same crispy views like the APO refractors.

Edited January 16, 2021 by KP82

[rajanp]

Thanks for all your replies and help here. I was trying to observe through a window and hadn't realised this affected the image so much - I took the scope outside for the first time and the detail in the moon looked great! Looking forward to seeing what some better eyepieces will deliver now!

[200pman]

I can recommend BST eyepieces.and good improvement over the supplied ones.

I have a full set of BST and they are very good.

Many people use them on this site.

I also have a 200p.

Which i will never sell.or upgrade unless i win the lottery.

[Spile]

I upgraded the stock oculars of my 200P with a Baader Hyperion IV zoom and Barlow combo. The flexibility and convenience works for me and the view is much improved. I chose this zoom based on reviews and positive comments made by users.

[rajanp]

How do you find the 5mm BST eyepiece with the 200P? I'm trying to figure out whether to get this or the 8mm first for looking at the moon and planets. 

[Kon]

15 minutes ago, rajanp said:

How do you find the 5mm BST eyepiece with the 200P? I'm trying to figure out whether to get this or the 8mm first for looking at the moon and planets. 

I have the SW 200P Dob and it is an excellent telescope. I am new here as well. So my thoughts are: the 25mm EP that came with it is fine, the 10mm Is pretty rubbish with me. The 25mm gets nice sharp stars. I added the 15mM and 8mm BST EP. The 15mm has seen a lot of action with DSO and the moon. The 8mm has been awesome for the moon and some DSOs.

 

13 hours ago, 200pman said:

I can recommend BST eyepieces.and good improvement over the supplied ones.

I have a full set of BST and they are very good.

I plan to upgrade on BST most of my EPs as well, so they pretty good budget EPs.

If I were you I would go for the 8mm since you will use it more unless you are more kin on planetary observation.

[Pixies]

28 minutes ago, rajanp said:

How do you find the 5mm BST eyepiece with the 200P? I'm trying to figure out whether to get this or the 8mm first for looking at the moon and planets. 

That would give you x240 magnification. Which  is usable of a night with very good seeing (for moon and double-stars), but I think you will find that it won't get used much.

I find I use the 12mm and 8mm EPs a lot. The latter for planetary. I'll barlow them very (VERY) occasionally when seeing is good - the 12mm more often than the 8mm.

[rajanp]

Yep that was my initial thought - I'd probably get some more use out of the 8mm given the 10mm that came with the scope doesn't seem as good as the 25. 

How necessary is a moon filter?

[johninderby]

Some find a moon filter neccessary but many don’t. It’s a very individual thing depending on your sensitivety to brightness. If you find the moon is too bright then get a filter.

I prefer the variable polarising filter as you can asjust it to your requirements. Also useful on Venus as well.

https://www.firstlightoptics.com/moon-neutral-density-filters/astro-essentials-nd96-0-9-1-25-moon-filter.html

https://www.firstlightoptics.com/moon-neutral-density-filters/astro-essentials-variable-polarising-moon-filter.html

 

[Ian McCallum]

14 hours ago, 200pman said:

I can recommend BST eyepieces.and good improvement over the supplied ones.

I have a full set of BST and they are very good.

Many people use them on this site.

I also have a 200p.

Which i will never sell.or upgrade unless i win the lottery.

Ditto. 👍