8" Dobsonian swap for 300p flextube ?

[Dazraz]

Hi

Have been thinking about getting a 12 " telescope and have just been offered a 300p flextube for my 8" Dob - is this worth it and is this a good telescope ?

Many thanks Daren

[gfletcher]

Snap his hand off Daren

Graham

[AndyBooth]

Agreed, you won't regret it at all.

[acey]

Why does he want to swap a 12-inch scope for an 8-inch?

[Dazraz]

Why does he want to swap a 12-inch scope for an 8-inch?

I am yet to see if he wants any cash on top

[dark knight]

sounds lika bargain, however I fail to see why someone would want to swap a 12" for an 8",,make sure you check the optics thoroughly first and if possible get a good viewing session with it first. You will also need to check collimation each time you use the flexitube, but that needn't be a problem.

Good luck

[Dazraz]

sounds lika bargain, however I fail to see why someone would want to swap a 12" for an 8",,make sure you check the optics thoroughly first and if possible get a good viewing session with it first. You will also need to check collimation each time you use the flexitube, but that needn't be a problem.

Good luck

Does collimation have to be done each time if the scope is left setup ?

[acey]

I am yet to see if he wants any cash on top

I expect he will.

You were asking in another thread about upgrading to a 12-inch and given the short amount of time you've had the 8-inch I'd still say stick with that.

I have a flextube 300p and it's an excellent scope for visual deep-sky work. I never use it in my garden because I find any kind of deep-sky viewing from a light-polluted area not worth the effort. Instead I put it in my car and drive to a dark site. It's big and heavy but manageable.

When I first got an 8-inch I thought it was huge but after 9 years it felt like a grab-and-go scope. When I first got the 12-inch a few months ago I thought it was huge, and still do. First thing I had to do was make a wheeled base for it so I could move it around my garage in one piece.

Planetary views with the 12-inch are no better than the views I had with my 8-inch (an Orion SkyQuest), and if anything slightly inferior. I notice more image shake at high-power with the 12-inch. If I were mainly looking at the Moon and planets then I would find the 8-inch preferable.

For best performance, the 12-inch needs full collimation (secondary and primary) every time you use it. It also needs a shroud to cut out stray light, and really needs some internal flocking too (I haven't done this yet).

It takes much longer than an 8-inch to cool down, so don't expect to plonk it on your lawn, do half an hour's observing, and put it away again.

If you plan on doing hours of visual deep-sky observing from a dark site, you won't be disappointed. If you plan on anything else, you might be.

First time I looked at M31 through my 8-inch I was disappointed. After a year or two of practice I could see the spiral arms of M51 with that scope. I said it in the other thread and will say it again - get to know the 8-inch before you upgrade.

[Dazraz]

I expect he will.

You were asking in another thread about upgrading to a 12-inch and given the short amount of time you've had the 8-inch I'd still say stick with that.

I have a flextube 300p and it's an excellent scope for visual deep-sky work. I never use it in my garden because I find any kind of deep-sky viewing from a light-polluted area not worth the effort. Instead I put it in my car and drive to a dark site. It's big and heavy but manageable.

When I first got an 8-inch I thought it was huge but after 9 years it felt like a grab-and-go scope. When I first got the 12-inch a few months ago I thought it was huge, and still do. First thing I had to do was make a wheeled base for it so I could move it around my garage in one piece.

Planetary views with the 12-inch are no better than the views I had with my 8-inch (an Orion SkyQuest), and if anything slightly inferior. I notice more image shake at high-power with the 12-inch. If I were mainly looking at the Moon and planets then I would find the 8-inch preferable.

For best performance, the 12-inch needs full collimation (secondary and primary) every time you use it. It also needs a shroud to cut out stray light, and really needs some internal flocking too (I haven't done this yet).

It takes much longer than an 8-inch to cool down, so don't expect to plonk it on your lawn, do half an hour's observing, and put it away again.

If you plan on doing hours of visual deep-sky observing from a dark site, you won't be disappointed. If you plan on anything else, you might be.

First time I looked at M31 through my 8-inch I was disappointed. After a year or two of practice I could see the spiral arms of M51 with that scope. I said it in the other thread and will say it again - get to know the 8-inch before you upgrade.

Yes i think i will take your advice and stick with my 8" the reason why i wanted to upgrade is because jupiter just looks a bit small to me and i would like to see more details and see its moon making a shadow on the surface but at the moment jupiter is just white and has a lot of glow - i can see slight detail but not a lot and m31 just looks the same as it does through my binos

ps the bloke with the swap wants £300 on top

[acey]

Jupiter does look small through a telescope - it's a case of trying to tease out the details.

If it's looking featureless there are a few possibilities:

Lack of practice

Poor atmoshperic conditions

Poor collimation

Stray light

Poor eyepiece

The first comes with time and the second varies. Planets will always look best when they're high in the sky, not near the horizon, and when the air is stable (maybe even with a bit of mist).

It's important to check collimation but with the 8-inch, once it's sorted, it'll stay in tune for a pretty long time. Also important not to get too hung up on collimation. Stray light is something you could think about further down the line (i.e. flocking) if other things (especially practice) don't improve your views.

Easiest thing is to upgrade your eyepiece, but again, I would advise waiting a bit.

I found that an 8mm TeleVue Plossl with my 8-inch gave excellent, contrasty planetary views. Cost around £50. I never went to higher magnification than that. I was able to see red spot, transiting moons etc. The high-power Plossl that came with the scope was considerably inferior.

A small number of good quality eyepieces is better than a lot of low quality ones. I've only ever bought 5 eyepieces (4 of them TeleVue Plossls) and I'm happy with them.

Regarding collimation, I didn't attempt it for the first year or so - I used a punctured film cannister to check alignment visually and reckoned it looked close enough. Once I started transporting the scope regularly I tried tweaking, still using a film cannister. I was able to collimate the scope well enough to see the discs of Jupiter's moons (a good test for an 8-inch). Eventually I bought a laser and cheshire and these really make the job easy once you know how to do it - but I got those with a view to using them on the larger, faster scope I intended upgrading to.

[Dazraz]

Jupiter does look small through a telescope - it's a case of trying to tease out the details.

If it's looking featureless there are a few possibilities:

Lack of practice

Poor atmoshperic conditions

Poor collimation

Stray light

Poor eyepiece

The first comes with time and the second varies. Planets will always look best when they're high in the sky, not near the horizon, and when the air is stable (maybe even with a bit of mist).

It's important to check collimation but with the 8-inch, once it's sorted, it'll stay in tune for a pretty long time. Also important not to get too hung up on collimation. Stray light is something you could think about further down the line (i.e. flocking) if other things (especially practice) don't improve your views.

Easiest thing is to upgrade your eyepiece, but again, I would advise waiting a bit.

I found that an 8mm TeleVue Plossl with my 8-inch gave excellent, contrasty planetary views. Cost around £50. I never went to higher magnification than that. I was able to see red spot, transiting moons etc. The high-power Plossl that came with the scope was considerably inferior.

A small number of good quality eyepieces is better than a lot of low quality ones. I've only ever bought 5 eyepieces (4 of them TeleVue Plossls) and I'm happy with them.

Regarding collimation, I didn't attempt it for the first year or so - I used a punctured film cannister to check alignment visually and reckoned it looked close enough. Once I started transporting the scope regularly I tried tweaking, still using a film cannister. I was able to collimate the scope well enough to see the discs of Jupiter's moons (a good test for an 8-inch). Eventually I bought a laser and cheshire and these really make the job easy once you know how to do it - but I got those with a view to using them on the larger, faster scope I intended upgrading to.

Thanks for the advise i feel im actually learning a bit now - first off whats flocking ?

I am going to a club next week and have also been told this is a great way to learn - cant wait !

[acey]

Flocking is lining the inside of the tube with a material of very low reflectivity (e.g. black felt). A project for the future.

Joining a club is a great idea and I'm sure you'll learn a lot.