Category : Astronomy Equipment

Canon 200mm 2.8 lens for widefield imaging

I have been trying out widefield imaging with the Geoptik adaptor and my Atik 460 mono camera using a relatively cheap Canon 75-300mm zoom lens. I have found that you need to step down the focal length to a more reasonable f6 or f7 to get some nice round star shapes. But really you want to me imaging at about f4 or f5. This means purchasing a more expensive camera lens like the Canon 200mm f2.8 or Canon 100mm f2.8.

I began looking at the beige Canon zoom lenses. I was interested in the 70-200mm 2.8 lens. Expensive new, but they can go for about £500-£600 used. I had been looking at the second hand market for a while. But what put me off is that I imaged in Ha and OIII at 100mm on my zoom lens and as you have to take apart the imaging train in order to change filters I found it impossible to not move the zoom when doing so.

This meant that the Ha images may have had a different Field of View compared to the OIII images. That’s usually not a problem you have with telescopes which are fixed. So a fixed prime lens did make more sense, plus it may be sharper.

As most of the widefield images I have taken are between 100mm and 200mm. I thought that a 200mm prime lens and a 100mm prime lens would do the trick. So I then started looking at the Canon 200mm f2.8 lens. I was trying to discount it as I had purchased the smaller version of the Telefokus to help me focus and the maximum diameter on those rings are around 78mm. I was worried that the rings would not fit around the barrel of the 200mm lens, but it turns out they do fit.

How I know is that I ended up buying a used Mk 1 version of the Canon 200mm prime f2.8 lens. I can’t see much difference between the Mk1 and Mk2, although the Mk1 does have an in-built lens hood.

The Canon 200mm f2.8 lens is a bit heavier – maybe more glass elements and a larger diameter is the reason.

I am yet to give the lens a go yet as it has been cloudy every night for the last week, but I’ll post some feedback and some images once I have used it.

canon 200mm f2-8 lens

Starlight Xpress Filter Wheel Constantly Rotating

Starlight Xpress USB Filter Wheel I went out last night, the first clear night in ages. The last time I had been out was the morning of the lunar eclipse. I was hoping the equipment was going to work straight away after not using it for a few months. The EQ8 mount was fine, the Lakeside focuser was working well, the Windows 10 PC was working well. But the Starlight Xpress filter wheel suddenly wouldn’t stop rotating.

I first tried just unplugging the USB cable and plugging it back in, that changed nothing. I then tried restarting the PC, that still didn’t work. I then looked on the Starlight Xpress website and downloaded the ASCOM v6.1 driver then I found the Starlight Xpress filter wheel firmware I had was 2 versions behind. So I installed the installer and managed to connect to the filter wheel and update the firmware. But even after doing this the wheel was still turning constantly.

I then tried a different USB port on the PC, but the PC did not even recognise the filter wheel. So my last option was to change the USB cable to a different one. I went straight from the filter wheel to the PC with the new USB cable into the same USB port on the PC and it worked. What I previously had was a USB extension cable and then a standard USB cable into the filter wheel. So I am still not sure if the USB extension cable was at fault (they usually are) or the standard USB cable.

Another thing to check is if the USB cable is loose in the back of the PC, as sometimes USB cables don’t fit very well into the back of the PC, they can be a very loose fitting. This may also be a problem if you are using a USB hub PCI card.

But if your Starlight Xpress filter wheel is constantly rotating check the USB cable is plugged in correctly, if that does not work try a different USB cable. As the power for the filter wheel is coming through the USB cable and you may have stepped on it and damaged it.

Here is a video on YouTube I made about the Starlight Xpress USB Filter Wheel problem.

ZWO ASI120MM S USB3.0 CMOS Astronomy Camera

Well I just got my ASI120MM S USB3.0 camera through via DHL. Ordered it direct from ZWO Optical on AliExpress and paid £250, then had to pay an extra £19 on import duty etc. But still a bit cheaper than buying from 365Astronomy – they were also out of stock at time of ordering.

The video shows below me unboxing it, and what it looks like.

This is a still image of my desk at 1280×960 on the ASI120MM S with the CCTV lens attached.

ASI120MM S USB3 Camera

I used the default capture software AMCap to get this still. Remember to install the correct drivers from the CD or from the ZWO website before you plug the camera into the PC.

ASI120MM S CMOS Camera

The CD is quite good it comes with ASCOM, PC drivers and ST4 software, as well as all the different ZWO camera driver versions. There is also some PC and Mac software on the disc. PHD2 and oaCapture for the Apple Mac and FireCapture and SharpCap as well as PHD2 for the PC.

I have now installed the camera on my observatory PC. The install was easy. I also installed the ASCOM drivers as well FireCapture and SharpCap 2.

I began with SharpCap 2, but found the best fps I could get was around 70fps at 640×480 (it was 30fps at 1280×960). Other people had reported around 100fps. So I loaded FireCapture – which I must say seems to have a lot more functionality than SharpCap.

I tried my tests again in FireCapture and at 640×480 I was now getting 106fps-116fps. So it seems which software you use makes a difference, unless some other settings were different.

It appears that the ASI120MM S is a very sharp camera and so far I am very impressed with it.

John Lewis Telescopes

Whilst I was searching lately for a new Skywatcher telescope I was amazed to see that John Lewis appeared in the lists on Google. So I had to have a look, John Lewis now sell telescopes. They don’t sell too many, about 7 in total. Maybe telescopes are becoming mainstream, maybe it’s the Brian Cox effect?

John Lewis currently stock the following telescopes:

Still a great Christmas present for the budding astronomer and a great place to start.

View all the John Lewis Telescopes

Second Hand Astronomy Equipment

I’m sure this is a highly emotive subject. But this is the question should you buy 2nd hand astronomy equipment?

I myself have bought and sold lots of astronomy equipment, either through AstroBuySell, Stargazers Lounge or eBay. But there seems to be so much astronomy equipment constantly on the second hand market, I wonder how many people have actually owned some of the items and how many ‘hands’ have touched them. I imagine there must be items that are constantly being passed onto the next person.

There are of course savings to be made on buying second hand equipment, which is the main reason we buy it. But sometimes it’s just nice to pay that little bit extra and have the assurance that you are buying new and that the item will come with at least a one year warranty.

The thing that makes me laugh is when people try to sell astronomy equipment when it only costs about another 10-20% to buy it new.

Selling your items not on eBay is the best thing to do as you don’t pay the eBay and PayPal commission, but I do think your items may go for a higher price on eBay just because of the number of visitors that eBay has.

You also have to watch out for dodgy astronomy sellers – they are out there. It’s always best when buying larger equipment to check the history of it, if you look on the archives in AstroBuySell or search the forum on Stargazers Lounge or search on Google, you may find some information on your item – especially if it has been bought or sold before.

Most astronomers look after there equipment very well, but I still like to have the end caps on an eyepiece and have the item boxed. That tells me that the owner has looked after the equipment, plus it means that the original box with help when I come to sell the item on.

Make sure the item works, and make sure the item is complete in everyway, it’s also advisable to see an image of the item when buying it. I have purchased a couple of items that did not work, like an illuminated reticule which did not illuminate! I asked the eBayer for a refund to help me fix it, but I did not get one. In the end I visited Maplin bought a new cable and an LED and fixed it.

If you are a seller and know something is wrong or missing, please be truthful and tell us about it, and don’t try and hide it and hope we as the buyer don’t find out about it.

Once you get hooked on the second hand astronomy items, I swear you never go back to new items unless you have to. I have lots of second hand equipment and I love it. But sometimes I wonder if I am mad, sending complete strangers hundreds of pounds for equipment I have never seen. So please think twice before buying, and if the item is over a couple of hundred pounds or so then why not visit the person and collect it – that is as long as it’s not too far away – especially with fuel costs being so high.

So should you buy 2nd hand astronomy equipment over new?