ETX-70 ED Petzval Astro snapshots

Took the modified ETX-70 out last 2 nights to take some snapshots (bottom of this message) All are stacks of 30 sec to 1 min subs. Per picture there is a couple of minutes of data that was stacked in DeepSkyStacker. No darks, no flats. Camera was set to do on the fly dark substraction. Post processing was also done in DSS. Camera is a modified Canon 1000d (filters removed only), mount was my LDX75.

I think I can get rid of some more CA by moving the Petzval lens closer to the front, but I do not feel like experimenting with that right now. It will not be my main imaging camera anyway. To make it more comfortable for visual use I modified an ETX erecting prism to fit a 1.25" fitting. Plus I added a generic RDF which does not attach to the scope but to the Manfrotto photo tripod.

Modified ETX-70 ED petzval

Hello world!

Huh? An ETX-70 ED Petzval?!

Yep. Ingredients: An ETX-70 OTA, a William Optics 66ED Petzval with a broken front lens, a GSO crayford style focuser + a lot of tinkering and voila:





From the WO 66ED I took the rear lens doublet which contains an ED lens (very likely FPL51) + the mounting bracket. The GSO focuser is from the 125mm achromat I gave up on. The ETX-70 OTA was removed from the mount. Only some cutting and driling was required, the GSO focuser exactly fits the ETX OTA. Cutting was required to reach focus. The WO rear lens doublet sits in the focuser (just as it was with the WO 66ED). To keep it there it is assembled in a baffling thingy I took from a Celestron focuser I had no other use for. Due to the wieght of the GSO focuser that is attched to the metal ETX-70 tube, the whole construction feels rock-solid.


Visually it is almost color free! Photographically there is color, more than with my Astro-Professional 102 ED refractor. It's about the same amount of color I had in my WO 66ED petzval. These are 30 seconds exposures (ISO 400):





Maybe future in it for my ideal grab-and-go astro snapshot astrograph ...

Scopes I'd buy again and scopes I wouldn't

Hello world!

Since the few years I have been busy with amateur astronomy I have owned several scopes and several types of scopes. What follows is based on personal experience and is not perse an authoritative review of the telescopes mentioned. I'll keep this simple and just go through the telescopes I have owned one by one. For each scope I will try explaining why I'd buy it again.

Meade ETX-70 / Meade ETX-80

This scope I would buy again. If you do not already own a telescope it would be a good starter scope in my opinion. I think, that the main advantages for a starter are the fact that it is highly portable and the fact that you can use it without knowing too much about 'the skies'. Portability is good, you can have the scope up and running in a matter of minutes after some practice. And once you have it up and running it's built-in goto computer will be your tour guide and not only show you the heavens, but it will even tell you about them.

What you should know is that the ETX is a short-tube and that because of this it will give you a wide field of view. This property is excellent for observing many deep-sky targets, but it will allow you to observe the moon and planets as well.

LOMO Astele 70 Maksutov OTA

This little telescope is everything the Meade ETX-70 and 80 are not: It is not a lens telescope but a combination of lenses and mirrors. It's not made of plastic, it's built as if it is supposed to survive a tank running over it. It is not American, it's Russian. Rather than being offered in every super market the Astele is hard to find (I suspect they are trying to avoid to sell as good as they can). And this is basically why I bought it. It's also very small and together with a tripod I can virtually bring it every where I go. I would buy this scope again, or even the 90mm variant if it would be available.

Meade DS-2130

This scope I would never buy again and as we speak it has been 'decommissioned'. I do however still own and use the goto mount with the Astele 70 and the ETX-90. The mount is very nice and durable when compared to the ETX-70/80.

The DS-2130 is advertised as a Newton type telescope (which means mirrors only, no lenses) but strictly speaking it's a catadioptric telescope or compound telescope. It combines a primary and secondary mirror with a little lens built into the focuser. The reason I bought this scope was aperture (130mm) so I would be able to 'detect' fainter deepsky objects than with the aperture limited ETX-70/80 and Astele. But frankly speaking I have hardly seen anything at all with this scope. The 'problem' with Newton scopes is that you need to collimate them - that is lining up the mirrors and the focuser. And the problem with the DS-2130 is that it makes this relatively simple process overly complicated due to the little lens I mentioned earlier. I have made many modifications to this scope (focuser, made lens removable, replaced the spider which holds the secondary mirror) only to find the images very disappointing.

Meade ETX-90 OTA

For new comers: OTA means 'optical tube assembly', so no mount and no tripod. I purchased it that way second hand and I only purchased because it was included with a bunch of Meade 4000 series and some WA oculairs. But the scope is very nice and I use it on the DS-2130 mount or even as a secondary scope on my LDX75 mount.

Shortly after I purchased this scope I saw a second hand modified Canon EOS 1000d for sale and I did my first astro photography experiments with the ETX-90 and a Meade 6.3 focal reducer.

Home built 125mm f/5.2 short tube achromatic refractor

With the DS-2130 being of no use I still had the desire for some more aperture mainly for deepsky and wide field observing. In between the ETX-90 and this scope I also acquired a Meade LDX75 equatorial mount. So when I saw this 125mm achromat offered I decide to purchase it. As expected this scope shows bright blue halos around bright objects. So although this scope is brilliant for wide and deepsky views, photographically it is severely handicapped.

It is currently configured as a Petzval using the secondary lens that came from a William Optics 66 ED Petzval which I purchased later. It still needs some work though.

I would buy this scope again.

William Optics Zenithstar 66 ED Petzval semi-APO

This scope I would not buy again, I have got nothing but frustration with it. My main complaint is with the coatings, they came off by simply looking at them. As it was no longer produced I could not swap it for another one and against better judgement I decided to keep it. Now Petzval design (2 doublet lens groups) implies that you get flat fields but I soon found out that this isn't the case with this Petzval. For improving flat fields I made modifications to the scope as they are described in the Yahoo William Optics group.

Astro-Professional 102 ED semi-APO

After all past experiences I decided I wanted a scope that I could actually use out-of-the-box, visually and photographically, and with decent aperture for a modest price. If I would start again with all current experience, and with a budget that would allow me to buy a LDX75 mount and the Astro-Professional 102 ED, I would buy this scope straight away and skip the rest. Which means I am pretty pleased with it.

BTW, the scope is also offered under many different brands, so what I write here also goes for the Orion 102 ED Premium, the William Optics Megrez 102 ED, and AstroTech 102 ED. And I am sure I can come up with a few more that are based on this exact same scope.

"First light"

Hello world!

I am a 42 year old computer programmer. I write data recovery software. About 3 years ago I purchased my first telescope, a Meade ETX-70, from a Lidl supermarket. The ETX saw first light at 'Ameland', a Dutch island, which compared to the main land gets pretty dark at night. As you may know the ETX-70 is a 'goto' scope and after aligning the scope I found myself taking the built-in tonight's best tour. Imagine, I had never done anything else than 'naked-eye' observations, basically nothing but the occasional look at the heavens. And then, this little scope showed me Saturn spot on! And that's where it all started.

Now, there are a lot of forums where people ask for advise; "ETX-70 or ETX-80 any good?" is a quite common question. And so often people get a negative answer to that question for various reasons, but let me tell you, if I'd have to start again I'd probably buy an ETX-70/80 again. As a matter of fact the ETX-70 was upgraded to the 80 model and I still use it. Yes, it is 'cheapish', yes, it is just an achromat, yes the aperture is only 80mm etc.. BUT, it's complete (unwrap packing and start observing right away - everything is there), it's light, views are more than decent, I can stuff it in a small backpack and I can take it everywhere. I'll do a little more on the ETX-70/80 later on. When in doubt, buy it.

I don't do it every night. So weeks can go by without me getting the scope out. But that first ETX got me hooked. Well, hooked, I am actually enjoying myself until this day. And this is what this blog will be all about. I am now somewhat experienced with several scopes and types of scopes and I have run into my share of problems with those. I have turned to others with problems and questions and I now hope I can return the favor to others.