miguel87

I am in 4 skies too, although I think it is generous when I compare other places that are bortle 4. I think very local light makes a difference e.g neighbours and streetlights. Luck to have bortle 3 less than an hour away on the brecon beacons. I only tend to go a couple of times a year but always amazing.

4 is great for a back yard 😁

An interesting bit of info about grass and heat. Amazing stuff! 🌱

I find dew problems alot worse observing over grass.

Also the reason more heat comes of the slabs is because they radiate it faster. So if you feel grass and slabs at midnight, the slabs will feel colder.

Under bright sun which looks brighter, slabs or grass. Slabs because they are reflecting the energy rather than absorbing it. I guess lighter coloured slabs are better than black ones!

1 hour ago, jambouk said:

As with everything in life, the answer isn’t binary.

After sunset, concrete emits the heat it has acquired during the daytime, much more than grass, so there will be heat currents drifting upwards and reducing the quality of the seeing around your telescope. So if you don’t care about the seeing setting up on concrete is fine. If you want the best possible seeing, don’t set up on concrete.

If you want perfect polar alignment then unless you have a permanent setup you’ll need to polar align each time you set up; so you’ll need to polar align if you set up on concrete or grass.

If you want to reduce vibrations transmitted from you walking around through the tripod and to the telescope, then I suspect grass would be better than slabs.

If you want the most stable surface to set up on I suspect slabs would be better than grass, but if you push the tripod legs into the grass firmly at the start, or use something to dissipate the load like anti vibration cups or caravan feet, then I doubt there would be any measurable differences.

James

Slabs are more stable, I dont have to realign each time at all. Grass creates way more damp, the grass can also move once you have polar aligned, vibration is non existent walking on well set slabs, worse on grass.

The ONLY downside of slabs is, like you say, the heat. Everybody I know would chose concrete over grass.

If the change is 30 degrees in 2000 years then I would suggest no.

That's about 0.015 degrees a year.

What you gonna measure this movement relative to? Because it will happen equally to all stars.

1 hour ago, lenscap said:

Hi Nick,

These coloured doubles will be easily seen in your Dob, no filters required.  

Your 8mm will be fine for these targets, (x150 in your 200p/F6). Have a look with your other eyepieces as well, and see which you prefer.

I had a good view of Izar recently at x140 in my 200p/F5 so your 8mm should split it if the seeing is good.

In poor seeing you may not get a clean split, but will still be able to see that it is a double with yellow & blue components.

How much colour you see depends on your eyes. I can see colours with both but much more vividly in my right eye than my left.

Enjoy.

Interesting about your eyes.

I have realised over time that I am VERY left eye dominant. Everything from colour, sharpness, position at the eyepiece and head stability are much better in my left eye.

I have tried to persevere with practicing my right eye viewing but it is just no good and very uncomfortable.

I can only speak from the DSLR side of things as I dont have experience with other cameras. With a DSLR in 'prime focus' (no lenses involved or barlows or anything) with a telescope, there is a set FOV which doesnt change and depends only on your camera and the focal length of your telescope (think of the dslr as one eyepiece).

As above, many images will talk about expensive mounts, star trackers and the level.of precision required but it is not really true, depending on the quality of photo you want.

People take great pictures with eq 2 or 3 mounts, dob mounts, non tracking mounts etc etc.

What camera are you using to image now? We might be able to work out how it compares to an average dslr in terms of FOV.

These pictures is not great, but, I love them. It's a photo of a glowing nebula which is light years away and I took it, on my own, from my back garden! 😁 that just blows my mind.

All were taken with my old cheap pentax dslr and a 200p on an unguided equatorial mount, just 1 exposure of 30 seconds. No processing on a computer, no stacking, they just came out of the camera as they are.

Good luck with the imaging.

Any idea where I might get the pucks from? I am tempted to just drill a couple of mill with an oversized drill bit and not get any brass picks, just use the slight recess in the slab?

2 minutes ago, DaveL59 said:

so I guess a can of fluorescent spray paint would be out of the question?  

How about boring into the patio slabs and putting in a brass disc at each leg position?

Spray paint might be my first option as I could probably get it off if needed.

Any idea what type would last more than a rain shower?!

Thanks mark. I thought about drilling but an worried I might crack a slab 😖

I consider myself very lucky to have a long dark garden with a raised patio at the back which is a lovely observing sight. I know the area of the patio which is flat test but I find that each time I set up and polar align I do have to make very minor altitude adjustments.

If I could somehow permanently mark 3 small spots on the patio to site the tripod legs, this would be avoided. However I dont know how I can mark them clearly and permanently without something so ugly that the mrs will kill me!

Any solutions?

2 minutes ago, Nick Sargeant said:

 Just had to educate myself on Bortle.. Another lesson learned..thanks Dr Strange

 

It's a good tool to use, when I first found out I was bortle 4 I though ok, that's pointless info!

But it's good for planning trips, if I see some accomodation or a campsite that sells itself as having dark skies I just find it on the light pollution map and can compare, if it's also 4 probably not worth the trip. If its 3 or better 2 I'm in!

Dont think I have ever been in a bortle 1. Unless camping in the Grand Canyon perhaps. Wasnt too into astronomy then tho.

2 minutes ago, Nick Sargeant said:

Wow,

bring on the darkness

 

The starguiders are great too as I'm sure you have heard. I love my 12mm 😁

3 minutes ago, Dr Strange said:

Yes, the 25 and 18 will do the trick. 

Yep you should just squeeze them all in the BST starguider. This only shows two because it has to be centred on one. The third is above.

4 minutes ago, John said:

 You want something that will show a true field of around 1.2 degrees. So a 20mm or 24mm SWA type eyepiece would do the job. Or a 30/32mm plossl.

 

Yes my error, I was using my 32mm not my 20mm. Good job I record details 😁

1 minute ago, Nick Sargeant said:

Sorry, it's dobsonian

thanks

 

So you will get a bit more magnification than me for any particular eyepiece. I would start with something in the 18-24mm range and go from there 👍

Of course if you have any super wide angle lenses you could zoom in further and still keep all 3 in frame.

Os it the dobsonian or on an EQ mount?

I have the 200p explorer on eq, with thay setup my 20mm eyepiece frames them pretty well with room to spare. Probably get away with down to about 15mm depending on your AFOV.

6 minutes ago, Dr Strange said:

Fascinating. Here in the US a cap is usually included... 

Should be really. I mean, how inexpensive is a little cap with a hole in?

13 minutes ago, Jakerm1995 said:

Hey, thanks for the offer. I am happy to purchase one today. But maybe I could ask if it's possible to come and watch you collimate? To get an understanding of how it is done, and also maybe try and grasp some other aspects of how dobsonians work.. I mean if that is okay with you of course I learn so much better when actually getting a hands on demonstration. 

 

Yep sounds good, a practical demonstration is always easiest plus it will be quicker with 2 people. On my current 200p I can reach the mirror screws whilst looking through the chesire so I can collimator myself.

I imagine your OTA length means you cant keep your eye on the focusser and reach the primary mirror at the same time. So 2 people is a bit quicker.

4 minutes ago, Dr Strange said:

Don't they at least give you a collimation cap?

I have purchased 5 or 6 telescopes and never had a chesire or collimation cap provided.

You can but it depends where you live. The hubble arbit doesnt vary more than 30 degrees north or south of the equator. So it's pretty much impossible to see from the UK as it's orbit is very low.

It's a common sight in north australia apparently.

Satellites move fast tho so alot of planning is needed to catch it for a fleeting second in a telescope.

1 hour ago, Jakerm1995 said:

I don't have a collimation tool, could you recommend any? I have read about a few, but am unsure exactly which one to go for. I've read that laser collimators can be inaccurate..?

Thanks,
Jake  

Yes chesire's are great, I have one you can borrow here if you like.

Lasers collimators have to be adjusted themselves so just something else that can go wrong. Chesire is super easy.

I know alot of people like astrobaby collimation instructions but personally I prefer http://www.propermotion.com/jwreed/ATM/Collimate/Chesire.htm

Love the telescope by the way.

Thanks everybody, it worked. Had to wait a while to get a gap in the cloud but i can acheive prime focus as long as no extension tubes are on the focusser.

These are just two single exposures on an unguided eq5, but it proves it works and I am happy 😁

I was gonna look at stacking etc etc but not sure I will bother, I like these basic snaps.

41 minutes ago, Shooting star said:

What would you say is the difference between the Vixen SLV and the Starguider eyepieces. How different a viewing experience is it? 

I dont wear glasses so I cant comment on that aspect.

There is no question that the SLV's have a slightly sharper image. But otherwise it's quite a close call. The extra 10 degrees AFOV in the starguiders is really nice to look at with very good stars almost right to the edge (my scope is f5 too). I slightly prefer the contrasty view through the starguider too, it could just be my eyes but the sky background is a very pleasing colour.

I bought the SLVs mostly for planetary stuff often paired up with my barlow so I wanted to get a quality lens what would put up with being barlowed at high magnifications.

But higher up the focal lengths, I would go for the BSTs everytime because the contrast and wider view are great.

17 minutes ago, Viktiste said:

The EOS 55D has close to the same "flange backfocus" as you Pentax K-r. So I am guessing you will achieve focus, but there is only about 1 cm left to move the focuser in. Bear in mind I have the stock focuser, I don't know the details of your focuser.

To find your field of view google your cameras pixel size and resolution and plug that and the 200P details in here: http://astronomy.tools/calculators/field_of_view/

I punched in the numbers (I think) and it seems a pretty good area, very similar to my 32mm eyepiece.