Demonperformer

Hi, Andy, and welcome to SGL.

I used nothing but a pair of 7x50s for decades. Still have them in my arsenal, and often get them out while the gear is imaging and just cruise the skies. Still come across new things.

The 200 dob is a great starter instrument. Is there an astro society near you (surely got to be one somewhere within striking distance of Bristol)? Before purchase, how about going along and seeing them. Societies often hold open "viewing" evenings when you would have the opportunity of having a look through various scopes. It would also give you a chance to see the physical bulk of some telescopes. I wish I had done that before purchasing a 10" dob (long gone now) ... totally unsuitable for my circumstances (although others get on with them very well). Nothing beats seeing a scope "in the flesh" for working out how well you will get on with it ...

Enjoy the journey.

I would hope a tracked mount is what is meant. Without any tracking, even 30s would be severely limiting in terms of focal length.

But you've got me thinking about PEC: apparently there are two sorts, one is dumb and the other reacts to what is happening "live". So, if you had been running an imaging session on an object, it would be learning what is happening to the mount in that session. This means that a sub taken at the end of the session would be more accurately tracked than one at the start of the session.

This is, as davew said, not as easy as it first appears ...

I am barely beginning to get to grips with CMOS ... I think I will join the "dinosaur" club and stick with what I have as well ... not that anyone will notice ...

An excellent challenge that could be a great "leveller".

A dark site is the astronomical equivalent of a unicorn.

50 minutes ago, noah4x4 said:

The only solution is turn off internal GPS  and use the hand controller for manual data input.

which defeats the whole object of paying extra for the gps system, surely.

Hopefully (?!) Celestron will be working on a solution ... although, as it was predicted, one might have hoped they would have produced a solution BEFORE it happened [sorry ... stupid suggestion ... where did i put my meds? ...]

On 16/10/2009 at 15:19, RobH said:

Gone are the days of the local ironmongers unfortunately, where you could buy nails by the pound, in eco friendly paper bags!

We still have one of those in Poole, Boones (they don't have a website but are listed on loads of the yelp-type sites). I can't praise them highly enough. They are the sort of shop you can go in with a nut and say "I want something that will fit this" and they find it and will sell you one. Brilliant.

1 hour ago, Jason D said:

It should look like that (with an offset). Here is a photo of my collimated scope

I stand corrected ... proved my first comment ("I am no expert")!

I am no expert on collimation (only just beginning to tackle it myself), but I think the black circle is supposed to be perfectly central and it looks offset to the right to me. I think this means you need to adjust the secondary a little.

Golden rule: whatever you do, do it in small (very small) steps, so that it is easy to reverse it.

On 15/03/2019 at 12:38, FLO said:

there aren’t many available

Does this mean they will become collectors' items and end up being worth 20x more than a boring old red one?

Great first photo. The only problem is that you have set the bar very high for yourself ... we will expect even greater things from you now

FLO are quite good ... drop them a query about it.

Are you going to be doing any imaging? If not, an AZ mount would probably be easier to work with than an EQ mount. Which one would depend on the scope, but I've seen reasonable reports of the SW-AZ4.

Some years ago I visited a cub camp with a scope for an evening. It was quite a dark location and, while setting up, I glanced upwards and had a quiet moan about the cloud that was invading a previously 100% clear sky - until I realised it was actually the summer milky way. Just not used to seeing any of it from home. 

On 03/03/2019 at 20:30, Peter Drew said:

wind farm turbines that now ringfence our location. 

is this going to become the new light pollution?

I wonder if it has anything to do with the increase in light pollution? Under a dark sky, you can see a lot more and under a heavy LP sky, even a small instrument, by darkening the background, simply enables you to simply "see" them.

This suggests a practical experiment for me: produce a 40mm mask for my 4" frac and take it out and compare what I can see with it "under the streetlights" compared with no instrumentation - a sort of "count the stars I can see in the Pleiades" sort of thing ...

Now, where's my "blue peter" kit?

7 hours ago, Stub Mandrel said:

There's a relatively new feature in PHD2 - you need the latest version - called 'predictive PEC' or PPEC. It 'learns' your system's behaviour over the first few cycles and then applies it, and  it constantly refines its model of the PEC. It does appear to work and I use it all the time now.

That is definitely worth investigating. Will go looking ...

Thanks.

Yes, I realise yours is, but not everyone on this forum has that luxury ...

Sorry, realise yours is permanent and wasn't trying to hijack the thread (much!), but the process obviously takes a significant amount of time and was wondering if it was still a worthwhile option when all the gear is put back together each session in not necessarily exactly the same relative positions. If PEC is working out of step it would be likely to cause more problems than it solves?

Great for a permanent setup, but is this worth doing on a temporary setup that has to be dismantled at the end of every session?

The backfocus on the 120 is 12.5mm.

The distance for whatever DSLR you have can be found here.

Most DSLRs seem to have a distance longer than 12.5mm, so achieving focus with the 120 may be possible.

As Steve suggests, a barlow may help with focus, but won't help with the camera's fov! Maybe an experiment for a night when the moon is around? - nice big target to hit and easy to see when focus is achieved.

Watched the video and it looks like a clever piece of kit. I'm not sure I like the helical focusser, but I guess as it doubles as a TP lens it makes sense.

Dear FLO

THIS IS A COMPLAINT

You know that I have already spent my annual allowance with you for this year.

I think it is extremely unfair that you should offer me such an irresistible goodie at a time like this.

This is your final warning!

That looks like a really neat arrangement. Nice one. I'm sure it will now start producing all sorts of clones on here ...

Mmm ... first thought was an animation of one of Jupy's moons disappearing into the planet's shadow under the heading "I'll be back" ... but I'm not sure that could squeezed into the rest of your description of what is required ...