TheSkySearchers

Any one try the larger objectives, 127mm for example, found at Surplus Shed? I want to build a 5" refractor some day using one.

A couple of forum folk have used this business for a refractor DIY project. Just remember to get a lens that says achromat (as opposed to just a single lens) and it is still hit or miss whether it is a quality lens or not.

Cheers,
JT

The 127mm Wollensak lens sets they sell are reported to be quite good and I have read many favorable reports over the years about them.
For the price I would think it would make a great project refractor with a good lens.

I forgot to mention, one thing that seems to be common with some of these 127mm is the lens sets may not be set properly.
Some people have reported that one or both lens are flipped but easy enough to fix yourself.

Lady Fraktor wrote: ↑Wed Nov 27, 2019 7:14 am The 127mm Wollensak lens sets they sell are reported to be quite good and I have read many favorable reports over the years about them.
For the price I would think it would make a great project refractor with a good lens.

I forgot to mention, one thing that seems to be common with some of these 127mm is the lens sets may not be set properly.
Some people have reported that one or both lens are flipped but easy enough to fix yourself.

Ah yes. Had the same problem with the 90mm from them, the crown was flipped. They also used tiny bits of plastic tape for the air space. I was not thrilled with the performance, so I replaced them with .006" aluminium shims. It took some experimenting with different thicknesses, but I got the chromatic and spherical aberrations down to a reasonable level. May not be a Unitron, but it easily reaches Dawes limit. And for $49 US on sale for the primary, it makes an excellent travel scope.

Thank you for the information, sounds like I may go through with it. It's eather a bigger newtonian, and mount, or a 5' refractor that will fit on the Edmund Scientific mount the 90mm is sitting on. It depends whether I put up an observatory or not, or not.

JayTee wrote: ↑Wed Nov 27, 2019 2:47 am A couple of forum folk have used this business for a refractor DIY project. Just remember to get a lens that says achromat (as opposed to just a single lens) and it is still hit or miss whether it is a quality lens or not.

Cheers,
JT

But of course, unless I go extreme retro and build a very, very long simple refractor. I have a big yard, but I think I will leave my amateur radio antennas up, instead.

I have built both of the 127mm's. The long focus in 2012 when the lens cell had the collimatable parts. Think it was the best mid f/# achro ever. I could go to 280x on the planets with the Antares 4.3mm W70 eyepiece. Over 300x it would color out the planets.

The 127 short was a recent one with no collimation rings. Glued wood rings to tube and cell with silicone to make a fast and easy collimation cell. It was the usual short achro performance with a maximum usuable power of around 180x. Made a good grab'n'go.