Remove focuser for transport?

[Astro_Bot]

I'm probably about to buy a crayford focuser for my "new" SCT. That'll make the overall length about 8cm more than without and, if I leave it on, it becomes very much harder to find a cheap plastic container that can be outfitted with equally cheap foam to safely transport the OTA, such are the dimensions of the tube. (I've spent a few hours measuring nearly every large plastic container in town - none will fit the OTA with focuser attached and still fit in my car).

I could build a custom crate, but I can't see that being any cheaper and my carpentry skills leave a lot to be desired.

It occurred to me that I could simply remove the focuser and attach/remove each evening - I suppose it adds 2 minutes to the process. But often when I draw these overly simple conclusions, I later find I've overlooked something obvious.

So, if I do attach/remove the focuser each evening, what trouble am I going to run into?

[MortonH]

I suppose there's a possibility that frequently attaching/removing the focuser might wear out the threads, or the fact that you expose the hole at the end of the ota while doing this.

For me the biggest issue would just be the hassle of doing it every time. I hate refractor cases that hold the ota but the diagonal has to be removed for transport, and diagonals just need to be slipped in, not screwed. I'm always trying to minimise the setup/teardown time, but maybe that's just my laziness.

[MortonH]

You didn't say why you are considering the Crayford. If it's just for visual you might consider something like this instead:

http://starlightinstruments.com/store/index.php?route=product/product&product_id=261

[Astro_Bot]

Thanks for the response.

I did look at the FT Micro, but I'd have to add a 2" visual back or another (SCT specific) diagonal as well, which bumps up the cost to equal a crayford (or thereabouts).

Besides that, with heavier mirrors (10"+), FT Micro's are reported to not remove all of the mirror flop, plus I may end up doing some AP with that OTA.

I may end up chancing my carpentry skills and building a custom crate, but it would be nice to be able to use an off-the-shelf plastic crate, though.

[MortonH]

Which SCT do you have? You can't be the first person to face this issue!

[Astro_Bot]

It's a Meade LX200-ACF 10".

Meade calls the focus knob "coarse" focus. Given it has a mirror lock, I figured I'd use it as advised - place the crayford in the centre of its range, focus (roughly) with coarse knob, lock mirror, then focus thereafter with the crayford (which should have enough range to cater for non-parfocal eyepieces). I envisage only having to alter coarse focus again if switching to AP or from AP to visual.

Another advantage of leaving the crayford fitted is that if I end up rigging a "cooler box" to aclimatise the OTA prior to use (a nascent idea - probably using my portable A/C unit to run cool dry air into an enclosure for an hour or so before heading outside, with a digital thermometer to let me adjust the interior ambient temp), then I can cool the crayford at the same time.

[MortonH]

Your plan is sound. Just the case that's a problem.

Maybe you could repost under a different subject heading that would catch more people's attention, e.g. "Case for 10" SCT - suggestions?". I'm sure you'll get some useful replies.

[Astro_Bot]

Thanks. I think I'll sleep on it and re-frame the question tomorrow, or perhaps everything will be clear by then.

After completing an associated chain of logic, I've placed an order for the crayford (a Moonlite).

[Stardrifter_WA]

Hi Astro Bot, I faced the same problem when I added a JMI NGT focuser to my 8" SCT. I love this focuser, however, I couldn't really keep removing it, as to position it properly, it had three tiny set screws. They later solved this problem with the Event Horizon focuser, which is rotatable. However, as Morton points out, taking it on and off may damage the threads over time, particularly if they become cross threaded.

In the end, I couldn't find a "cheap" solution to this problem either, particularly since I wanted to ensure the proper protection for my equipment. After much thought I sought an alternative solution. I realised that I would never probably sell my equipment, so I had a proper road case made. These cases also use High Density foam which is much more durable and more protective than the soft foams.

Although this isn't really a "cheap" solution, it certainly was the best solution in terms of protecting my "valuable" equipment. The dimensions where such that it would fit in the boot of my car (Commodore). I also use a fold up trolley to move it around.

I looked around until I found the cheapest manufacturer. It cost $650 which was "relatively cheap", when considering the value of the equipment it protects and what other manufacturers were charging. It was made in such a way that I could also store tube counterweights, without them moving within the case.

Sometimes trying to find a cheap solution isn't always to the best, at least, that is what I have found over many years of experience. When I had this case made, I couldn't really afford it either, but I am now certainly happy that I went to the extra expense.




Hi Morton, I had the same problem, so I also had a case made that would fit the diagonal. It cost $350 with all the machined inserts. Next year I will have to get another one made to take my new FLT110.

Cheers Peter