Astromania Guide Scope 50mm FMC Compact Finderscope Guide Scope Kit with Double Helical Focuser Compatible with 1.25 inch Eyepiece for Astronomical Telescope & Auto Guiding Camera for Astrophotography

I have the 70mm version and found this to be good quality optical instrument and a great guide scope - for folks who have a long FL main scope. There are other (and cheaper) FLs available. I bought a 0.5 FL reducer just in case – but haven’t used it, yet. Good dew shield, great worm focuser, well-built at 2.5 lbs and only about $160. To my surprise, for beginners who don’t want to spend too much money before they know they truly love Astrophotography and can master and afford it, it also makes for a decent primary scope (which is why I bought it – replace “beginner” with not-so-sure “returner”). Before you stop me and ask: “What about chromatic aberration? What about distortions around the edge of the field-of-view?” Well, the answer is: surprisingly, there isn’t all that much of that. This is actually a great beginner’s main scope if attached to a good (perhaps used, low $$ automated mound), a steady tripod, and a decent camera. Below, I will discuss three images I have recently taken. All are on the ZWO TC40 tripod with the ZWO AM5 automated mount using the ASIAIR PLUS mini-computer interface, and with a ZWO ASI 585MC camera. Note of caution: in that configuration, make sure the scope sits high up on the mount and does not easily run into the tripod. I am using a triple Vixen extender of which I have sawed off one offending member – but even then in that configuration the scope needs to be high on the Vixen receptacle to not run into the tripod. I live in the SF Bay area, so there is a lot of light pollution. Often I cannot even see Polaris with my bare eyes (and yes, I know it's a variable star :). All images were taken at a gain of 301; 200 images taken total, processed with DeepSkyStacker, Graxpert, and GIMP. All without a guide scope (through which I obviously took these images). Inexpensive SvBONY IR and UV cut-off filter to reduce dispersion. M53: Here I was mainly testing this guide scope’s optics. And since w/o guide scope, I used only 3s exposures to avoid star trails due to wind and mount tracking errors. DeepSkyStacker does not like short exposures, especially if there is a bright object in the frame (here: the core of the cluster). I needed to reduce the percentage of max light that is used for detecting stars for stacking: 10% is normal (about 3-4 stars, here; 5% not enough (about 5 stars, here); and 2% gives 7-10 stars, with only about 50% of 200 stacked images acceptable – which I picked; with drizzle set to zero for crisp dim stars. I think you will agree the image is great for this type and price of telescope. Leo Triplet: 90% of 200 exposure at 20s (no guiding, of course). Looks good to me, given the 70 mm aperture and the limited exposure time. M101: 148 of the 200 exposures where deemed good enough. Here you can see the problem when not taking “darks” at high contrast settings in GIMP: hot pixels and striations – but I did not care, for the purpose at hand. Edit: M101, another version: Same as before but now with a Celestron X-Cel LX 3x Barlow (!), and a ZWO ASI533MC Pro USB 3.0 Color camera. Using the 26 "best" out of 70 3m (180s) light exposures, gain 101, T = 0°C, 20 3m (180s) dark exposures, gain 101, T = 0C = 1h . FL should be 3x400 = 1,200mm but ASIAIR says it's 1,370mm. That happens with Barlows and varying back focus... and it is a problem: it means the effective magnification is not 3x, but 1370/400 = 3.425; or a relative light loss of 3.42^2 -- almost 12 instead of the nine I expected. So, bear that in mind - there wasn't enough light to use DSS to stack, but ASTAP worked fine.

This is a wonderful device and would be so at double the price. Build quality is outstanding. The focuser employs both a drawtube and helical unit, for coarse and fine focus respectively. Both have fine gradations so focus can be dialed in directly. The construction is metal throughout, and the aluminum adjuster screws have nylon tips that will not mar the satin black finish of the tube. Coatings on the cemented 60mm achromat are a deep green and very uniform. One assumes this is basically a binocular objective so it remains to be seen how well it will perform at high power visually, but of course as an auto-guider or finder such considerations are irrelevant. One complaint, the drawtube inner surface is quite shiny and required flocking. The unit can be used with a prism diagonal if one inserts a Barlow between it and the diagonal. This allows the scope to function as a high-power visual right-angle guide scope. Note however that the unit will not focus at infinity with any diagonal unless a Barlow is inserted before the diagonal. When I insert a Meade 2x Barlow and prism diagonal + 40mm Plossl eyepiece, I measure a 4mm exit pupil, giving an effective f/ratio of 10 and effective focal length of 600mm, which is right in line with a typical 60mm x 700mm traditional guide scope. One can substitute a roof prism diagonal for a naturally oriented image. Used this way the scope becomes a passable spotting scope. The one obvious improvement to the scope would be to make the tube from two pieces, one of which could be removed to allow focus with a diagonal without inserting a Barlow. This is a minor point in my opinion, one has a finder after all for low power views - this is a versatile, well-made device and I highly recommend it.

For the money it seems fine for viewfinder/guide scope. Focuser works smoothly. Front lens cap is a floppy rubber thing that won't stay on. Mount is solid. Alignment screws will ding scope up if you get carried away tightening them.

Replaced the spotting scope on my Celestron telescope. Nice field of view.

Optics are decent, not good enough for a standalone scope, but OK for a guide scope. Workmanship, machining, and finishes are top notch ... the coarse and fine focusing are excellent. Mount rings are effective and well made. Major issue ... it does accept 1-1/4 eyepieces, but don't think you can use a 90-degree diagonal ... it just doesn't have the focusing range for this. This leaves a somewhat awkward viewing posture with the scope mounted flush with the telescope tube.

Very good as imaging scope for astrophotography to get a wide field.

La calidad de hechura es buena, no sirve para hacer fotografía adicional como campo amplio por lo que es muy específico para su funcion

Excelente calidad, excelente producto, super bien protegido para transporte y llegó super mega rápido!!! gracias!!!