Luke

As John says, when Sarah and I moved from a 12 inch dob (F5) to a 16 (F4.4), it became obvious there was a problem for us with the 35mm Panoptic. It was very washed out for us, which was a shame, as it is a beautiful eyepiece. We then found out that the high exit pupil was the problem, thanks to SGL and John!   I suppose it was still usable for the less faint stuff, but it pained me to see such a good eye piece not at its best.

We now realise the 35mm was also a bit washed out before in our F5 dob, even under darker skies than home at the SGL star party. At the time, we just thought that was what wide, low-power eyepieces were like.

Don't some people measure their pupil in the dark? (I assume with a touch of red light so they can see the measurement!). I definitely don't have barn owl eyes

Thanks, James, I wasn't sure how to go about stacking multiple DSLR moon shots. Look forward to giving it a go!

I know cheap scopes get a bad press, as they can put people off, but in our case, a £35 scope from Jessops was to blame. Just an impulse buy while checking out camera lenses. One view of the moon was all it took! The mount was wobbly, but it goes down as one of the best things I ever got for under £100.

Does anyone know how I would get my Hutech 2" IDAS LP filter into the lightpath somehow please with an OAG

Two ways seemed to work okay for me but I am not an expert on spacings. I just tried them and was happy with them for me:

- A low profile SCT to 2" adapter with filter thread between the Celestron 6.3 reducer and a 2 inch adapter on the visual back. I think it was this one:

http://www.firstligh...ct-adaptor.html

This was okay until I wanted to use a 2" Ha filter, which would have made the guide stars too faint for the guide camera after being savaged by the Ha filter, I think. So I bought some bits from the ROT system from Teleskop Service to go between the DSLR and OAG:

https://www.teleskop...OS-bayonet.html

I've only used a Celestron Radial guider. Very happy with it, nice and solid, a decent amount of movement on the guide camera arm to rotate it around to help find a guide star. I'd buy the same again, though I can't compare it to other OAGs.

I'd recommend heater strips if you can squeeze in the cost. They are not cheap but I'm so glad I got some, you can spend hours and hours imaging and with dew heaters it's one less thing to worry about going wrong! (unless like me you forget to turn up the heat enough one time!...)

Almost all orders we have placed with Teleskop Service and showing as in stock on the TS website have been dispatched the same day and have arrived two working days later in the UK with UPS delivery.

All email enquiries have been answered promptly in clear English with no language barrier. The replies have always been helpful.

Almost all orders have been completely smoothly. There were minor problems with two orders that TS resolved immediately.

The vast majority of our orders with FLO have been trouble-free. More often that not the gear is received the next day, and any delay, I have been able to check the progress of the order online.

On the rare occasions when things have gone wrong, usually not FLO's fault, FLO has sorted problems quickly:

- We ordered an ST80 guidescope. The foucser was damanged in transit. FLO sent out a replacement immediately. Fedex delivered the replacement the next day and picked up the faulty one.

- We ordered a Rigel Quikfinder and it broke. Immediately replaced by FLO, who said drop off the old one at the star party we were going to.

- Problem with puck on NEQ6 - immediately replaced by FLO, drop off the problem one at the star party.

- Some scratches on a base plate for a focuser, immediately replaced by FLO.

- Screws not included with an ADM saddle. Martin at FLO contacted ADM for us and sourced the correct screws.

Also, FLO has helped source things we were having difficulty finding:

- We wanted a plastic holder for a handset. FLO sourced one for us.

- We wanted a Losmany dual mounting bar with dual saddles at each end. There wasn't such a thing at the time, FLO got one made for us.

The amount of magnification is the focal length of the telescope divided by the focal length of the eyepiece.

For example, my 100mm refractor has a focal length of 900mm.

A 10mm eyepiece would give 900/10 = 90x magnification.

A 20mm eyepiece would give 900/20 = 45x magnification.

So as John says, the higher the eyepiece number, the lower the magnification.

In our 100mm we love looking at the planets, splitting some double stars, looking at the moon, some of the brighter DSOs like the Orion Nebula - especially the trapezium stars - and some of the brighter clusters like the Beehive and Double Cluster.

I think if you are using a ladder then in all seriousness it is too late, there is nothing that can be done to help. However, I wish I was as ill as you. Where's my lotto ticket?

Folks are incredibly hard to convince, sometimes, that f ratio is what determines exposure time.

It took me over a year to work that one out! I was fairly convinced that a huge aperture F10 SCT would image faster than a small aperture, fast scope. But the penny finally dropped a few weeks back.

Here's how it makes sense to me, please correct me if I am wrong:

Ignoring things such as differences in contrast, take these two scopes:

1) 80mm refractor, focal length 500mm, fairly fast at F6.25.

2) 280mm SCT, focal length 2800mm, slow at F10.

Penny drop #1:

At prime focus - no barlows, reducers, ... - how zoomed in you are on an object depends on the telescope's focal length, nothing else. A bit like on a camera's 50-300mm zoom lens, 300 gets you in way closer than 50.

So at prime focus, objects look 5.6 times bigger in the SCT (2800mm / 500mm).

Penny drop #2:

When you switch from prime focus to using a 2x barlow to double up the image size, the amount of time you need to get the same brightness of image is not double, it is FOUR times as long an exposure.

A bit like if you have an image in Photoshop, such as 100x100 pixels, if you double it up in size, it actually takes up four times as many pixels (100x100 = 1000, versus 200x200 = 4000).

Penny drop #3:

Although the SCT has over 12 times the light grasp of the 80mm refractor (280mm squared / 80mm squared), objects are 5.6 times bigger in the SCT, which works out that they cover over 30 times as many pixels (5.6 * 5.6).

12 times more light versus sharing the light over 30 times as many pixels - that's why the SCT needs a longer exposure - 12 times more light in, but spread over 30 times the number of pixels.

Final penny drop:

Of course, while the refractor is faster, it is nowhere near as zoomed in at prime focus. Imagine if your target needs the zoom of the SCT. To get the equivalent zoom in the 80mm, you'd need to use something like a 5x barlow,which would take 5x5 = 25 times longer to expose than the usual prime focus exposure. So if you are using an SLR in particular and want to get in close on small targets, the SCT could come into its own then, this is presumably why some imagers use a refractor for bigger targets and the SCT for the small, faint things.