TS Imaging-Star 'scopes?

[DaveS]

Just an idle query at present. I know that the Imaging-Star 71 also by WO has a good reputation, but looking at the TS flat-field apo page there looks to be several flat-field 'scope ranging up to 130mm, in a 3+3 configuration.

So, how good are they? Has anyone any experience of those other than the 71mm version?

I'm not buying just yet, but could be in the market for something shorter than 400mm and the Borg 89 f/4.3 looks good, as does the 80mm f/4.4 imaging star (2+4 vs 3+3).

Wondering too what the 130 f/5 has over the 130 P-DS to justify the price difference.

[DaveS]

Hmm... 3 days, 125 views, no replies.

So either nobody has bothered with anything beyond the Imaging Star 71, which is a known, very good, scope, or my question was so wooly as to preclude an answer.

Therefore I'll rephrase it:

I currently image with either a Megrez 90 + FR at 497 (Call it 500) mm or a 130 P-DS at 650 mm, both around f/5. I'll be looking (When I can justify spending) for something enough shorter than 500 to be worthwhile, thinking about 375 mm or so, while being fast. I was looking at the Imaging Star 80 f/4.4 or (A bit longer and more expensive) the Borg 89 f/4.3. I have considered the Esprit 80 with flattener but at 400 mm fl it's a bit in between. I looked at the Vixen 100 mm f/3.8 but I don't want to spend that kind of money just yet and it's a bit fast for my Astrodons.

Can anyone comment on my ideas, or have any other possibilities that I haven't thought of?

I may also be looking at something longer than 650 mm, preferably a 'frac, as I don't like spikes and I'm a bit frightened of the 190 MN as I'm rather to cack-handed to fettle and collimate one. I'm almost completely NB as the LP in London makes LRGB a little problematic, even with a LP filter in the train so perfect apochromatism isn't vital, but flat-field is.

[Davey-T]

I like the look of the 130mm Dave, I think you should buy one and do a review 

Dave

[ollypenrice]

I know personally of several people who have bought variant brands of the Star 71 and had to send them back for replacement. There is clearly a significant QC issue. However, a good one is a good one and in all cases the replacements have been good. The main thing, then is to buy one of these from a supplier known not to mess customers about over problems and returns.

I have never come across any images posted from the other flatfield apos you mention. Have you tried a Google search for any? Maybe not many are yet circulating? Ole Alexander has posted good images from the TS100Q, however.

I was more than happy with my Tak Baby Q which could get down to 328mm and 44mm circle. Several others on here have been just as happy though a couple of disappointing ones have been discussed in a recent thread.

My feeling about the Borgs is that they would be better for NB than broadband because the blue channel is not well controlled in images I've seen. I've never used one or seen one here so this based entirely on looking at images.

For a big refractor the TEC140 takes a lot of beating once you have the dedicated flattener in place. FL is, according to plate solving, a tad longer than the 980mm of the spec. No currently available CCD chip can put its flat field into difficulty and if ever one appears you'd probably need to sell you house to pay for it! It covers my full format CCD very easily.

Olly

[DaveS]

Thanks Dave and Olly

Yes, the fact that I've seen so little mention of the other 'scopes suggests a degree of rarity, though the spot diagrams given for the 80 and 102 suggest also a well controlled field to the corners of a 35 mm sensor. Wonder why they don't include one for the 130? 

Since I anticipate being almost entirely NB the Borg becomes an option provided the field is as flat as advertised. Another possibility for the long end is the Vixen 140 SSF but it's a touch slow at f/5.7. At £1400 it's also a heck of a lot cheaper than a TEC.

[Davey-T]

Had a browse around forums and image sites and couldn't find a single image taken with the 130mm.

Dave

[DaveS]

No. me neither. TBH I'm not sure what it has to justify the price multiple over the humble 130 P-DS. I did find an image of sorts taken with the 102 mm, but it's not really in my spending plan, it would only make sense as a direct replacement for my Meg 90.

Still, I have so many expensive non-astro projects coming up that any astro spending will have to be very well justified. In fact, the only thing I have planned is an imaging shed for my 'scopes.

[ollypenrice]

Plenty of scopes are cheaper than the TEC140 and some are quite a lot more expensive, but how many are better? 

Olly

[DaveS]

Well, after much dithering I have finally pushed the button on an Imaging Star 80mm f/4.4 flat-field sextuplet.

It's something I can afford / justify, and my HEQ5 will carry it quite happily, something I wouldn't be too sure of with anything of "galaxy" focal length. It will give me the whole of the Rosette or M42+Running Man on my 694 sensor, without being so fast as to compromise my 3 nm Astrodons.